Preheat oven to 350°F (175°C). Line a rimmed baking sheet with parchment paper or foil and lightly grease.
Heat olive oil in a medium skillet over medium heat. Sauté the onion and green bell pepper until softened, about 5 to 7 minutes. Set aside to cool completely.
Crush the Ritz crackers in a zip-lock bag with a rolling pin or pulse in a food processor until fine crumbs form.
In a large mixing bowl, combine eggs, crushed Ritz crackers, shredded cheddar, milk, salt, pepper, garlic powder, and paprika. Stir until the crackers absorb the liquid.
Crumble ground beef over the cracker-egg mixture and add the cooled vegetables. Use clean hands to gently mix until just combined. Do not overmix.
Let the mixture rest for 5 to 10 minutes. Shape into a 10-inch by 5-inch loaf on the prepared baking sheet.
Bake uncovered for 30 minutes. Do not open the oven during the first 20 minutes.
While baking, mix ketchup, brown sugar, and yellow mustard in a small bowl until smooth.
After 30 minutes, remove meatloaf and brush the glaze generously over the top and sides. Return to oven and bake until internal temperature reaches 160°F (71°C), about 30 to 40 more minutes.
Remove from oven, tent with foil, and rest for at least 10 to 15 minutes before slicing.