In a large skillet over medium heat, brown the ground beef with the diced onion until fully cooked and onions are softened. Drain excess grease.
Stir in taco seasoning and ¼ cup water. Reduce heat to low and simmer 3–5 minutes until thickened. Remove from heat.
In a separate skillet, heat the oil over medium-high heat. Fry each tortilla for about 30 seconds per side until golden and crispy. Transfer to a paper towel-lined plate to drain.
Preheat oven to 400°F / 200°C. Line a sheet pan with parchment paper.
Assemble each pizza by spreading refried beans on one tortilla, adding seasoned beef, then a sprinkle of cheese. Top with a second tortilla.
Spread enchilada sauce over the top tortilla and sprinkle with additional cheese.
Repeat to make 6 pizzas and place on prepared sheet pan.
Bake for 6–8 minutes, or until cheese is melted and bubbly.
Remove from oven and top with chopped tomatoes and green onions. Serve immediately.
