Slice the tops off each bell pepper and set the tops aside, since you'll use them as lids later. Scoop out the seeds and white membrane with a spoon until the inside is clean. Trim a thin sliver off the bottom if a pepper wobbles, so it can stand up straight in the dish.
Using your paring knife, cut simple triangle eyes and a jagged mouth into one side of each pepper. Keep the cuts small since bigger openings let the filling spill out while baking. Work slowly here, the peppers are sturdier than they look and give you time to get the shapes right.
Heat olive oil in a large skillet over medium heat and add the diced onion. Cook until softened, then add the ground beef and garlic, breaking the meat apart as it browns. Stir in the tomato sauce, cooked rice, Italian seasoning, garlic powder, onion powder, salt, and pepper.
Preheat your oven to 375°F while the filling finishes cooking on the stove. Spoon the meat and rice mixture into each carved pepper, pressing gently to fill every gap. Top with shredded cheddar cheese before setting the lids back on top of each pepper.
Pour the ¼ cup of water into the bottom of the baking dish to keep things moist. Cover the dish loosely with foil and bake for about 30 minutes until the peppers soften. Remove the foil for the final 10 minutes so the cheese can melt and turn golden.
Let the peppers sit for five minutes once they come out of the oven before moving them. This short rest helps the filling set slightly so it doesn't fall apart on the plate. Serve them standing upright with their carved faces on full display for the table.