In a skillet add half of the oil, 2/3 of the red peppers, and the onion, sautéing until tender, about 15 minutes.
Add the garlic and tomato and sauté for another 5 minutes. Remove from heat and cool for 10 minutes.
Into a food processor add the rest of the ingredients along with the remaining 1/3 of red peppers, and the cooled pepper mixture. Pulse until combined.
With machine running, add in the remaining 2 Tbsp of oil. Continue to puree for another 30 seconds until sauce is smooth. Season to taste with salt.
Notes
*for dairy free, replace cheeses with 1/2 cup full fat canned coconut milk