user153: Is there a way to use cardano-cli (or another tool) to query a Cardano node for an NFT's current owner (wallet address holding the NFT)?
The parameters for such a query would likely be the Policy ID & Asset Name of the NFT.
Since, from a blockchain perspective, there is no difference between native tokens for which an arbitrary amount of tokens exist and those where there is only a single one (NFTs), I guess a query like the one I'm looking for is not something that fits into the grand scheme of things; but maybe I'm missing something?
If there is no tool readily available, how could I use cardano-cli (or another tool) to look through all transactions (starting with the most recent and going backwards in time) until I find the most recent transaction containing the NFT in question?

user153: As suggested by Marek, blockfrost.io seems to be a great way to jump right in.
For an alternative do-it-yourself way other tools can be used.
Using cardano-db-sync the blockchain data acquired by a Cardano node will be fed into a PostgreSQL database, allowing to query the data through SQL.
Querying that database looks like this (this is just a random query taken from the example queries, it does not answer the original question):
select tx_out.* from tx_out
inner join tx_in on tx_out.tx_id = tx_in.tx_out_id
inner join tx on tx.id = tx_in.tx_in_id and tx_in.tx_out_index = tx_out.index
where tx.hash = '\xf9c0997afc8159dbe0568eadf0823112e0cc29cd097c8dc939ff44c372388bc0' ;

   id    | tx_id  | index |        address          |    value     |        address_raw        | payment_cred
---------+--------+-------+-------------------------+--------------+---------------------------+--------------
 2195714 | 996126 |     4 | DdzFFzCqrh...dtq1FQQSCN | 158685237964 | \x82d8185842...1a330b42df |

Building on that, one could further set up cardano-graphql to provide a GraphQL API for cardano-db-sync. This is what the Cardano Explorer is built upon.
Using cardano-graphql, a query to find the current owner of a given token could look like this:
query TokenOwner($policy_id : Hash28Hex, $asset_name : String) {
  utxos (where: {tokens: {_and: {asset: {policyId: {_eq: $policy_id} assetName: {_eq: $asset_name}}}}})
  { 
    txHash
    address
    value
    tokens {asset {policyId assetName} quantity}
  }
}

Where the arguments denoting the NFT are its policy id and asset name, for example:
{
  "policy_id": "d5e6bf0500378d4f0da4e8dde6becec7621cd8cbf5cbb9b87013d4cc",
  "asset_name": "537061636542756433373430"
}

Note that asset_name is provided in hex format.
For this example, a random SpaceBud (SpaceBud759) with no other tokens in the UTXO was selected, resulting in the following output (on 2021-05-02) where the address field denotes the current owner:
{
  "data": {
    "utxos": [
      {
        "txHash": "4fcf200a8b18f866bd4e9324600ffe636b081d79a9bb06b748fa41947f3a6a5e",
        "address": "addr1qxjtqaxmv44u2zx02v7658wrlt87tv9yp7knzwh6hana3ra5ay9tjpf6e0d3p2t7s6gnnqtwmva02lx4p0dlx8a7x8uqrw46dy",
        "value": "1500000",
        "tokens": [
          {
            "asset": {
              "policyId": "d5e6bf0500378d4f0da4e8dde6becec7621cd8cbf5cbb9b87013d4cc",
              "assetName": "5370616365427564373539"
            },
            "quantity": "1"
          }
        ]
      }
    ]
  }
}

As of writing, using the policy id in queries like shown above seems to be non-functional, as described in this github issue.
Further example queries can found here, one might also check out this graphical representation of the API.

user28: There is no way to find that information without syncing the whole blockchain into a database with a tool such as cardano-db-sync.
This takes a lot of time and resources, so you might want to use an API like blockfrost.io to query the addresses owning a specific token.
$ curl  -s -H "Project_id: $BLOCKFROST_PROJECT_ID" https://cardano-mainnet.blockfrost.io/api/v0/assets/00000002df633853f6a47465c9496721d2d5b1291b8398016c0e87ae6e7574636f696e/addresses | jq
  [
   {
    "address": "addr1qxlmfhfcjck5pctuvlpww3kuxvqjucz40qusgeqgmyqq4utntgjccmteyrsldd67rxv2yq6ew2a7t48q34p9j7nf0kjqskku78",
    "quantity": "1"
   }
  ]


153: <p>Is there a way to use <code>cardano-cli</code> (or another tool) to query a Cardano node for an NFT's current owner (wallet address holding the NFT)?
The parameters for such a query would likely be the <em>Policy ID</em> &amp; <em>Asset Name</em> of the NFT.</p>
<p>Since, from a blockchain perspective, there is no difference between native tokens for which an arbitrary amount of tokens exist and those where there is only a single one (NFTs), I guess a query like the one I'm looking for is not something that fits into the grand scheme of things; but maybe I'm missing something?</p>
<p>If there is no tool readily available, how could I use <code>cardano-cli</code> (or another tool) to look through all transactions (starting with the most recent and going backwards in time) until I find the most recent transaction containing the NFT in question?</p>
 153: <p>As suggested by Marek, <a href="https://blockfrost.io" rel="nofollow noreferrer">blockfrost.io</a> seems to be a great way to jump right in.<br />
For an alternative do-it-yourself way other tools can be used.</p>
<p>Using <strong><a href="https://github.com/input-output-hk/cardano-db-sync" rel="nofollow noreferrer">cardano-db-sync</a></strong> the blockchain data acquired by a Cardano node will be fed into a PostgreSQL database, allowing to query the data through SQL.</p>
<p>Querying that database looks like this (this is just a random query taken from the <a href="https://github.com/input-output-hk/cardano-db-sync/blob/master/doc/interesting-queries.md" rel="nofollow noreferrer">example queries</a>, it does not answer the original question):</p>
<pre><code>select tx_out.* from tx_out
inner join tx_in on tx_out.tx_id = tx_in.tx_out_id
inner join tx on tx.id = tx_in.tx_in_id and tx_in.tx_out_index = tx_out.index
where tx.hash = '\xf9c0997afc8159dbe0568eadf0823112e0cc29cd097c8dc939ff44c372388bc0' ;

   id    | tx_id  | index |        address          |    value     |        address_raw        | payment_cred
---------+--------+-------+-------------------------+--------------+---------------------------+--------------
 2195714 | 996126 |     4 | DdzFFzCqrh...dtq1FQQSCN | 158685237964 | \x82d8185842...1a330b42df |
</code></pre>
<p>Building on that, one could further set up <strong><a href="https://github.com/input-output-hk/cardano-graphql" rel="nofollow noreferrer">cardano-graphql</a></strong> to provide a GraphQL API for <code>cardano-db-sync</code>. This is what the <a href="https://explorer.cardano.org/" rel="nofollow noreferrer">Cardano Explorer</a> is built upon.</p>
<p>Using <code>cardano-graphql</code>, a query to find the current owner of a given token could look like this:</p>
<pre><code>query TokenOwner($policy_id : Hash28Hex, $asset_name : String) {
  utxos (where: {tokens: {_and: {asset: {policyId: {_eq: $policy_id} assetName: {_eq: $asset_name}}}}})
  { 
    txHash
    address
    value
    tokens {asset {policyId assetName} quantity}
  }
}
</code></pre>
<p>Where the arguments denoting the NFT are its <em>policy id</em> and <em>asset name</em>, for example:</p>
<pre><code>{
  &quot;policy_id&quot;: &quot;d5e6bf0500378d4f0da4e8dde6becec7621cd8cbf5cbb9b87013d4cc&quot;,
  &quot;asset_name&quot;: &quot;537061636542756433373430&quot;
}
</code></pre>
<p>Note that <code>asset_name</code> is provided in hex format.</p>
<p>For this example, a random SpaceBud (SpaceBud759) with no other tokens in the UTXO was selected, resulting in the following output (on 2021-05-02) where the <code>address</code> field denotes the current owner:</p>
<pre><code>{
  &quot;data&quot;: {
    &quot;utxos&quot;: [
      {
        &quot;txHash&quot;: &quot;4fcf200a8b18f866bd4e9324600ffe636b081d79a9bb06b748fa41947f3a6a5e&quot;,
        &quot;address&quot;: &quot;addr1qxjtqaxmv44u2zx02v7658wrlt87tv9yp7knzwh6hana3ra5ay9tjpf6e0d3p2t7s6gnnqtwmva02lx4p0dlx8a7x8uqrw46dy&quot;,
        &quot;value&quot;: &quot;1500000&quot;,
        &quot;tokens&quot;: [
          {
            &quot;asset&quot;: {
              &quot;policyId&quot;: &quot;d5e6bf0500378d4f0da4e8dde6becec7621cd8cbf5cbb9b87013d4cc&quot;,
              &quot;assetName&quot;: &quot;5370616365427564373539&quot;
            },
            &quot;quantity&quot;: &quot;1&quot;
          }
        ]
      }
    ]
  }
}
</code></pre>
<p>As of writing, using the <em>policy id</em> in queries like shown above seems to be non-functional, as described in this <a href="https://github.com/input-output-hk/cardano-graphql/issues/485" rel="nofollow noreferrer">github issue</a>.</p>
<p>Further example queries can found <a href="https://github.com/input-output-hk/cardano-graphql/tree/master/packages/api-cardano-db-hasura/src/example_queries" rel="nofollow noreferrer">here</a>, one might also check out <a href="https://input-output-hk.github.io/cardano-graphql/" rel="nofollow noreferrer">this graphical representation</a> of the API.</p>
 28: <p>There is no way to find that information without syncing the whole blockchain into a database with a tool such as <code>cardano-db-sync</code>.</p>
<p>This takes a lot of time and resources, so you might want to use an API like <a href="https://blockfrost.io/" rel="noreferrer">blockfrost.io</a> to query the addresses owning a specific token.</p>
<pre><code>$ curl  -s -H &quot;Project_id: $BLOCKFROST_PROJECT_ID&quot; https://cardano-mainnet.blockfrost.io/api/v0/assets/00000002df633853f6a47465c9496721d2d5b1291b8398016c0e87ae6e7574636f696e/addresses | jq
  [
   {
    &quot;address&quot;: &quot;addr1qxlmfhfcjck5pctuvlpww3kuxvqjucz40qusgeqgmyqq4utntgjccmteyrsldd67rxv2yq6ew2a7t48q34p9j7nf0kjqskku78&quot;,
    &quot;quantity&quot;: &quot;1&quot;
   }
  ]
</code></pre>
