Cut into wedges. In a large bowl, mix together the lemon juice, mustard and dried rosemary. Season to taste with the salt and pepper. When well combined, add the olive oil and mix through.    {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/0\/0d\/Roast-Onions-Step-14Bullet1-Version-2.jpg\/v4-460px-Roast-Onions-Step-14Bullet1-Version-2.jpg","bigUrl":"\/images\/thumb\/0\/0d\/Roast-Onions-Step-14Bullet1-Version-2.jpg\/aid2623728-v4-728px-Roast-Onions-Step-14Bullet1-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":"728","bigHeight":"546","licensing":"<div class=\"mw-parser-output\"><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"https:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a> (screenshot)<br>\n<\/p><\/div>"} Cover thoroughly.  Bake for 30-45 minutes or until well browned and tender. Season to taste and serve.

Summary:
Preheat the oven to 400ºF/200ºC. Peel the onions. Make the dressing. Toss the onion wedges in the bowl of dressing. Arrange the covered onion wedges on a baking sheet or dish. Place in the preheated oven. Remove from the oven.