Wash tomatoes. Cut in half (doesn't matter in which direction.) Turn over, spray bottoms lightly with 1 spray of cooking spray.
Turn all halves cut side up. Spray lightly with 1 spray of cooking spray. Sprinkle with ground black pepper and your choices of dried or fresh herb or herbs, such as: parsley, oregano, basil, thyme, rosemary, sage, etc.
Place tomato halves into top tray (or snack tray) of Actifry cut-side up. (No need to spray the top tray.) Turn Actifry on for 20 minutes. (In a basket-type air fryer, try 160 C / 320 F with no preheat for 20 minutes.) After 20 minutes, check for doneness, which will vary based on size of tomatoes, how many halves you are actually doing at once, ripeness of tomatoes, your personal preference, etc. If needed, give them another few minutes.
Tip! If you are making a meal for which you also require the bottom Actifry bowl, cook the grilled tomato halves to 20 minutes, remove top pan from Actifry, proceed with cooking in the bottom bowl, then when everything else is ready, just place the top pan with the tomatoes back in for a 2 minute reheat.