Preheat your oven to 350°F (175°C).

In a skillet, heat a splash of oil over medium heat. Add chopped onions and green bell pepper, sautéing for about 5-7 minutes until soft and translucent.

In a large bowl, combine ground beef, crushed Ritz crackers, sharp cheddar cheese, sautéed vegetables, milk, ketchup, and balsamic vinegar. Mix gently.

Transfer the mixture into a greased loaf pan or shape it into a loaf on a baking sheet.

Spread ketchup over the top of the meatloaf as a glaze, optionally mixing in some balsamic vinegar.

Bake for approximately 1 hour, until the internal temperature reaches 160°F (71°C).

Let the meatloaf rest for 10-15 minutes before slicing to ensure tenderness.