Cube potatoes and bell pepper into small cubes - about 1/4" on each side. Combine salt, pepper, chili powder, smoked paprika, and onion powder in a small bowl. Toss potatoes and peppers in the avocado oil and then the seasoning blend. Toss until each piece is evenly coated in the seasoning.
Preheat air fryer to 400F for about 5 minutes. Pour half of the seasoned potatoes and bell pepper into the air fryer basket or tray. I find these cook best if you cook them in two batches.
Cook potatoes in the air fryer at 400F for 8 minutes. Toss the potatoes and cook for another 7 minutes. Remove that batch of potatoes from the air fryer and repeat with the second batch. **The second batch may cook faster. Taste the potatoes and season with additional coarse sea salt to taste.