Preheat the oven to 350°F (175°C).
Melt 1 tablespoon of the butter in a large skillet over medium-high heat. Add the shredded cabbage and sauté until softened, about 4–6 minutes. Remove the cabbage from the skillet and set aside in a bowl.
Add the remaining 1 tablespoon of butter to the same skillet. Add the ground beef and cook over medium-high heat, breaking it up with a spoon, until browned and cooked through, about 6–8 minutes.
Stir in the taco seasoning and dried minced onion. If the meat seems dry, add up to 1/4 cup water and stir to combine. Cook 1–2 minutes more so the seasoning is distributed.
Return the sautéed cabbage to the skillet, season with salt and pepper to taste, and fold in 1/2 cup of the Mexican cheese blend until combined.
Sprinkle the remaining cheese evenly over the top of the skillet mixture. Transfer the skillet to the preheated oven and bake until the cheese is melted, about 10 minutes.
Remove from the oven and let rest for a couple of minutes before serving.