Preheat the oven to 350° and lightly grease a 9×13 casserole dish. (This casserole can actually be cooked right in the 12-inch skillet that you use to cook beef and vegetables or in a separate 9×13 casserole dish.)
Slice onions and bell peppers and saute until softened. Add tomatoes and garlic and saute until garlic is fragrant.
Take vegetables out of the pan, and set aside. Saute ground beef in the same pan as the vegetables, breaking up all the clumps until beef is browned.
Mix cooked vegetables back into the beef.
Add spices, diced chili in adobo sauce, tomato sauce, salt, and sugar. Mix well, pour in hot beef stock, and add rice. Stir everything until evenly incorporated. You can cook beef and rice mixture right in the skillet or transfer it into a casserole dish at this point.
Cover the casserole dish tightly (or the skillet) with a sheet of aluminum foil and bake for about 40 minutes. (Note: if using different rice, bake time could be a few minutes more or less.)
Take the dish out of the oven and take off the foil. Sprinkle cheese evenly over the top of the casserole and bake for another 5-7 minutes.
Notes
Long grain white rice: long grain rice tends to cook fluffy and as separate grains.Long grain rice includes American long-grain rice, Basmati, and Jasmine rice. (Medium grain rice also cooks as separate grain but more moist and tender. Short grain rice tends to clump together. Medium grain rice includes Arborio rice and short grain rice includes sushi rice.)
Make it more spicy: If you want to make the casserole more spicy, don’t add more chili peppers in adobo sauce because that will make the dish more bitter vs spicy. To increase spice, you can add a spicy chili pepper (or two) to the dish, like jalapeno or serrano and you can leave the seeds in to increase the heat level.
Want to use brown rice? You can use long-grain brown rice! You’ll need to adjust the cooking time as brown rice takes longer (and sometimes much longer) to cook. A rice casserole using brown rice could take up to 60 minutes of covered bake time.