Preheat the oven to 350 degrees.
Heat 1 tablespoon of olive oil in a skillet over medium-high heat. Add the onion, and saute for 2-3 minutes when the onions begin to soften.
Add in the minced garlic, and stir for 30 seconds.
Toss in the ground beef, and break it up, stirring often while it browns.
Mix in 1 tablespoon of chili powder.
Add in the onion powder, paprika and cumin. Stir the meat mixture well, and continue to cook it until it is completely browned.
Slice each bell pepper in half, and remove the insides along with the seeds.
Place the bell peppers halves cut side up into a casserole or high sided baking dish.
Fill each bell pepper half with the meat mixture. It is okay to heap the mixture up over the top of the bell pepper if needed.
Top the meat filled pepper halves with 1 cup of shredded cheddar cheese.
Bake the peppers in the oven for 25-30 minutes until the cheese has melted, and the peppers are starting to turn tender.
Remove the peppers from the oven, top with shredded lettuce, diced tomato and sour cream.