Prep the peppers. Slice each bell pepper in half lengthwise, straight through the stem. Remove the seeds and white ribs.
Brown the beef. Cook the ground beef in a skillet over medium-high heat for 6 to 8 minutes, breaking it up as it cooks, until no pink remains. Drain the fat. (Skillet-free option: air fry the beef in the 2.5-qt glass container at 375°F for 12 minutes, stirring every 4 minutes. Drain.)
Season and mix. Stir the cumin, salt, and garlic powder into the hot beef. Add the drained diced tomatoes with green chilis, then fold in the cooked Spanish rice and ½ cup of the Colby Jack cheese.
Pre-crisp the peppers. Arrange the pepper halves cut side up in a single layer in the 6-qt container. Air fry at 375°F for 5 minutes.
Stuff and cook. Pack the filling into each pepper half, mounding slightly. Air fry at 375°F for 10 minutes.
Add the cheese. Top with the remaining 1 cup of Colby Jack and air fry at 375°F for 3 more minutes, until the cheese is bubbling with golden-brown spots.
Rest and serve. Let the peppers rest 5 minutes before serving — the filling is molten straight out of the machine.