Preheat oven to 375°F (190°C) and line a baking sheet with parchment paper.

In a bowl, season ground beef with salt and pepper; shape into 8 small patties.

Heat a skillet over medium-high heat; cook patties for 3-4 minutes per side, adding cheese slices during the last minute to melt.

Slice slider buns in half and toast cut-side up in the oven for about 5 minutes until golden brown.

Assemble sliders by placing each patty on a bun bottom; add onions, ketchup, and mustard.

Serve warm and enjoy!