Ground Beef Mac and Cheese Casserole

regular boxed macaroni and cheese (like Kraft original), reserve cheese packet

olive oil

chopped onion

chopped green or red bell pepper , or use a combination of both

large clove of garlic , chopped

ground beef

chili powder , or to taste (can omit if using Rotel)

seasoning salt (like Lawry's )

( 14.5 ounce ) can regular or fire-roasted diced tomatoes , undrained

Kosher salt and freshly cracked black pepper ,

shredded pepper jack, cheddar cheese or your favorite cheese, optional