Chop tomatoes, onion, and zucchini into evenly sized pieces. Arrange in a 9x13 baking dish along with the garlic cloves. Drizzle olive oil over the top, then season with salt. Tuck in fresh oregano.
Roast for 60-90 minutes, until vegetables are soft and edges are lightly caramelized.
Let cool slightly. Scoop into a blender or food processor and add a handful of fresh basil and cracked black pepper to taste. Vent the lid and purée until smooth, or leave with a little texture if you prefer. Taste and adjust seasoning.
Handful fresh basil, Cracked black pepper
Pour into containers and cool to room temperature before storing in the refrigerator or freezing.