Given a paragraph about cooking, and a set of conversational question answers about the paragraph, generate a relevant question to the topic of the paragraph. The paragraph has the prefix 'CONTEXT:'. Each conversation question has a prefix `Q:` followed by the answer prefix `A:`.
Q: CONTEXT: One of the first things I learned in Indian cooking is that the combination of tomatoes, onions and ginger is self-thickening. As time went by, I realised that the thickening effect is far more noticable with old varieties of tomatoes - "beef" tomatoes and a lot of the modern varieties are difficult to thicken unless partially fried first.Despite the absence of ginger, I suspect that the thickening is purely a natural action between the tomatoes and the onion, and that the tomatoes used were some particularly nice old variety.  <sep>  Q: Why did my tomato soup turn thick and brownish? A: One of the first things I learned in Indian cooking is that the combination of tomatoes, onions and ginger is self-thickening  Q: The above combination with garlic, onions, spices can't be all wrong, can it? A: beef" tomatoes and a lot of the modern varieties are difficult to thicken unless partially fried first 
A: 
Do tomatoes have to be skinned?