Preheat your oven to 375 degrees. While it heats, slice the tomatoes in half, onion into quarters, and deseed and halve the peppers.
Toss in avocado oil & arrange on a sheet pan, sprinkle with salt.
Roast for 30 minutes, adding the garlic cloves (unpeeled) with about 10 minutes left. Remove from the oven & let cool