Prepare the Tomatoes: Start by preheating your oven to 400°F (200°C). Slice the yellow tomatoes in half and arrange them on a baking sheet. Drizzle with olive oil, and sprinkle with a pinch of salt and pepper. Roast for 20-25 minutes, or until the tomatoes are soft and slightly caramelized. This roasting step helps intensify the flavor of the tomatoes.
Cook the Aromatics: While the tomatoes are roasting, heat a tablespoon of olive oil in a large skillet over medium heat. It will take about 5 to 7 minutes of cooking after adding the chopped onion until it is soft and clear. After you add the chopped garlic, cook for one more minute or until the food smells good.
Blend the Sauce: Once the roasted tomatoes are done, remove them from the oven and let them cool slightly. Using a blender or food processor, puree the roasted tomatoes until smooth. You can leave it a bit chunky if you prefer texture in your sauce.
Combine and Simmer: Pour the tomato puree into the skillet with the cooked onions and garlic. Stir in the oregano, basil, salt, pepper, and sugar (if using). Let the sauce simmer over low heat for 15-20 minutes to allow the flavors to meld together.
Finish the Sauce: If you prefer a creamy yellow spaghetti sauce, stir in the heavy cream or half-and-half. For added richness, you can also fold in some grated Parmesan cheese at this stage. Simmer for an additional 5 minutes, then taste and adjust the seasoning as needed.
Serve: Toss the sauce with freshly cooked spaghetti or your favorite pasta. If you want, you can add fresh mint and extra Parmesan cheese as a garnish.