1. Fire up your Ooni pizza oven.
2. Meanwhile, place the onion, tomatoes, bell peppers and rosemary in a bowl and toss with a drizzle of olive oil.
3. Once the pan is hot, add a little oil to the pan, followed by the onion mixture and cook for 1-2 minutes, or until lightly caramelised.
4. Remove the pan from your Ooni, top with the feta and pine nuts, then cook for another minute, or until the feta has started to melt.