Wash the roma tomatoes and cut them in half lengthwise. Use a small spoon to scoop out the seeds and the watery pulp in the center. Removing the excess moisture is important because it significantly speeds up the drying process.
Place the tomato halves on a cutting board cut-side up. Drizzle the olive oil over them, then sprinkle with the salt, dried oregano, garlic powder, black pepper, and sugar. The sugar helps concentrate their natural sweetness as they dry.
Preheat your air fryer to 200 degrees F.
Arrange the tomato halves in the air fryer basket cut-side up in a single layer. You may need to work in batches depending on the basket size. Cook at 200 degrees F for 1 hour.
Check the tomatoes and gently flip them over. Continue cooking at 200 degrees F for another 1 hour to 1 hour and 30 minutes, checking every 30 minutes. The tomatoes are done when they are shriveled, deep red, and leathery but still slightly pliable - not completely brittle.
Remove the sun dried tomatoes from the air fryer and let them cool completely on a wire rack. Store them in an airtight jar covered with olive oil in the refrigerator for up to 2 weeks, or freeze them dry in a zip-top bag for up to 3 months.