PREHEAT your oven to 375 degrees F. Lightly coat a 9×13-inch baking dish with nonstick spray or EVOO. Slice the bell peppers in half from top to bottom down through the stem. Remove the seeds and membranes then arrange cut side up in the prepared baking dish.
HEAT oil In a large skillet over medium heat. Cook onion until soft, about 5 minutes. Stir in tomato paste and garlic and cook until fragrant, about 1 minute more.
STIR in the Italian seasoning, cumin, garlic powder, salt, and pepper. Let cook 30 seconds.
STIR in the spinach a few handfuls at a time, cooking until wilted down; this will take between 1 and 2 minutes.
POUR in the can of diced tomatoes along with the juices. Let simmer for 1 minute. Then add in your chopped Kretschmar Roast Beef.
REMOVE the pan from the heat. Stir in the rice (or your grain of choice), 1/4 cup of the cheddar, and 1/4 cup of the pepper jack. Add salt and pepper to taste.
MOUND the filling inside your bell pepper halves, then top with the remaining cheeses.
POUR a bit of water into the pan with the peppers carefully - just enough to barely cover the bottom of the pan.
BAKE the stuffed peppers uncovered for 30 to 35 minutes, until the peppers are tender and the cheese on top is melted. Garnish with parsley or cilantro. Serve hot and top with csour cream if you please.
TO STORE: Refrigerate stuffed peppers in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a baking dish in the oven at 350 degrees F.
TO FREEZE: Freeze peppers in an airtight freezer-safe storage container for up to 3 months. Let thaw overnight in the refrigerator before reheating.