Preheat your oven according to the Texas toast package instructions. (Trust me, don’t skip this—it matters.)
Place the toast slices on a baking sheet and bake until golden, flipping halfway if needed.
Meanwhile, in a skillet over medium heat, brown the ground beef with the chopped onion. Drain the grease if you're not into extra shine.
Add ketchup, brown sugar, mustard, Worcestershire sauce, salt, and pepper. Stir it all together and let it simmer until thick and glossy.
Scoop that sloppy goodness onto your toasted bread, top with shredded cheese, and pop them back in the oven just long enough to melt everything together.
Serve immediately—preferably with a side of napkins and zero judgment for seconds (or thirds).