Mix onion, olives, capers, garlic, ½ teaspoon salt, and a few grinds pepper in an 8 X 8-inch baking dish.
Stir in 1 tablespoon olive oil, then top onion mixture with thyme sprigs.
Core tomatoes, then lightly score an "X" on both ends. Cut in half, then place cut side down on top of thyme sprigs. Drizzle tomatoes with remaining tablespoon olive oil.
Bake until tomato skins are shriveled and onions are tender (about 35 to 40 minutes).
Peel off and discard tomato skins, then transfer tomatoes to blender (or food processor). Remove thyme sprigs, then add onion mixture to blender as well.
Pulse sauce a few times or until chunky. Stir in 1 teaspoon fresh thyme leaves, and season to taste with salt and pepper.
Serve sauce tossed with pasta, as a dipping sauce, and more. Enjoy!
Notes
This recipe makes about 3 cups / 24 ounces / 700 milliliters of sauce, or about 6 half-cup servings. It's enough for 1 pound of pasta.For the tastiest sauce, select the freshest, most flavorful tomatoes you can find. I used heirloom tomatoes, but tomatoes fresh from the garden or the farmers market can also be used. You could even use roma or plum tomatoes in a pinch.The texture of this sauce is easy to customize. For a chunkier sauce, pulse it just a few times. For a more uniform sauce, blend it until smooth.Don't forget to check out the info before this recipe card for helpful tips, variations, serving suggestions, and more!