Preheat oven to 350°F (175°C) and line a baking sheet or loaf pan with parchment paper.
In a large bowl, combine the ground beef, diced onion, bell pepper, grated carrots, crushed Ritz crackers, shredded cheddar cheese, beaten eggs, milk, and 1/4 cup of the ketchup. Mix gently until just combined; do not overmix.
Shape the meat mixture into a loaf on the prepared baking sheet, or press evenly into the loaf pan.
Bake in the preheated oven for 30 minutes.
While baking, whisk together the remaining 1/4 cup ketchup, brown sugar, and mustard to create the sweet and savory glaze.
Remove the meatloaf from the oven, brush the glaze evenly over the top, and return to the oven to bake for an additional 25-30 minutes, or until the internal temperature reaches 160°F (71°C).
Let the meatloaf rest for 10 minutes before slicing. Garnish with chopped fresh parsley before serving.