Preheat the oven to 175℃/155℃ fan (350℉/310℉).
Toss the tomatoes in the oil and mixed herbs. Tip into a roasting dish and arrange in one layer. Roast for 20 minutes, or until well cooked, tossing halfway through. Alternatively air fry for 170℃/340℉ for around 10 minutes, or until well roasted. Toss half way through.
Meanwhile, make the whipped feta and avocado. Add all of the ingredients for the whipped feta and avocado to a food processor. Process on a high speed until creamy. Taste and add more salt, pepper, lemon, juice, and/or olive oil to taste.
Toast your sourdough and spread each slice with the whipped avocado and feta. Top each slice with 6 tomatoes and season with salt and pepper. Sprinkle over the fresh chives and squeeze over a little more lemon juice. Enjoy!