In a skillet over medium-high heat, cook the ground beef and diced onions until the beef is browned and fully cooked, about 8 minutes. Drain any excess grease.

Return the beef mixture to the skillet, add taco seasoning, and stir in 3/4 cup of water. Bring to a simmer, then reduce heat and let it simmer until the liquid has mostly evaporated, about 5 minutes.

On two baking sheets lined with parchment paper, spread a generous layer of tortilla chips.

Dollop refried beans over the chips, dividing evenly between the two baking sheets.

Evenly distribute the seasoned ground beef on top of the chips and beans.

Cover with shredded cheese blend.

Bake in the preheated oven for 15 minutes, or until the cheese is melted and bubbly.

Remove from the oven and immediately sprinkle diced tomatoes and sliced green onions over the top.

Serve hot and enjoy your epic beef nachos supreme!