Preheat oven to 400℉. Line a quarter sheet pan (note 1) with aluminum foil. Set aside.
In the bowl of a food processor, add the green pepper and onion and pulse until finely chopped. Transfer to a large mixing bowl. Add the oregano, thyme, paprika, cumin (optional), garlic, salt, and pepper. Stir to combine.
Add the meat and gently mix. Use a fork to prevent overworking the meat. (Note 2)
Transfer the mixture to the prepared pan and shape into a brick approx. 4x8 inches.
Bake for 30 minutes. Meanwhile, in a small bowl, combine the ketchup, mustard, and brown sugar.
Brush the ketchup glaze over the top of the meatloaf. Bake until the internal temperature reaches 160℉, approx. another 10-15 minutes.
Let the meatloaf rest for 5-10 minutes before slicing.
Notes
A sheet pan or shallow casserole dish is best for cooking meatloaf because it allows the heat to circulate around the meatloaf. Avoid using deep meatloaf pans because the meat will steam and won't brown or caramelize around the edges.
Work the meat as little as possible to prevent a dense, tough loaf. Mix all of the seasonings together first, before adding the meat. Also, use a fork to gently mix the meat into the seasonings.