Preheat oven to 450 degrees (F).
Take your roma tomatoes and emove parts attached to stem then cut into quarters. Place on your oven safe dish.
Chop onion into large pieces and place under the tomatoes to prevent burning.
Drizzle tomatoes and onions with olive oil and place in the oven for 20-30 minutes. Until easily pierced with a fork and the edges slightly browning.
Once that is done, place all ingredients in a blender (avocado flesh removed from skin and seed), or in a pot, and blend for 1 1/2 minutes.
Serve warm or store in the fridge for up to 3 days or freeze for up to 30 days.