Preheat oven to 350. Allow the oven to fully come up to temperature so the meatloaf cooks evenly from the start, helping it set properly and retain moisture.
Beat the eggs in a large mixing bowl until the yolks and whites are fully combined and slightly frothy. This helps the mixture bind more smoothly. Add the milk and the crushed Ritz crackers, stirring until the crackers begin absorbing the liquid and softening. This creates the tender texture typical of this style of meatloaf.
Stir in the chopped onion and shredded sharp cheddar cheese. Distribute them evenly so each slice has balanced flavor and texture. The onion should be chopped fine enough to soften during baking without leaving raw pieces, while the cheese should be well mixed so it melts uniformly.
Add the ground beef, along with the salt and pepper. Gently mix the ingredients together using clean hands or a large spoon, folding rather than aggressively kneading to avoid compacting the meat. Overmixing can cause a dense loaf, so stop as soon as everything is just combined.
Shape the mixture into a loaf on a lightly greased baking pan or in a baking dish. Form it tightly enough to hold its shape but not so tightly that it becomes packed. A loaf with a slightly rounded top helps the glaze cling and caramelize attractively.
Bake at 350 for 45 minutes. During this initial bake, the loaf will begin to firm up, render some juices, and brown slightly around the edges. This stage sets the structure so the topping can later be applied without sinking.
Meanwhile, combine the ketchup, brown sugar, and mustard to make the topping. Stir until smooth. The mixture should be thick but pourable, forming a glossy glaze that caramelizes in the oven.
Spoon half of the topping over the meatloaf after 30 minutes of baking. Apply it gently so you don’t disturb the surface. At this point, the loaf should be firm enough to support the glaze without breaking apart.
Return the loaf to the oven for 10 more minutes of baking, allowing the first layer of topping to set and begin bubbling at the edges. This helps build a flavorful, slightly sticky coating.
Spoon the rest of the topping over the meatloaf, spreading it evenly across the top. Return to the oven and bake for 5–10 minutes more, just until the glaze fully melts, darkens slightly, and becomes glossy. Avoid overbaking at this stage to keep the loaf moist.
