Heat a dry pan over medium heat and preheat the oven to 350*F.
Sprinkle the sliced beef, sliced pepper, and sliced onions liberally with salt, then add to the pan and cook on the stovetop, tossing often with tongs or a wooden spoon, until the beef has mostly cooked through and browned and is slightly pink in the middle.
While the beef is cooking, make the enchilada sauce: In another saucepan, heat the oil over medium heat.
Whisk in the flour and chili powder until no lumps remain, then whisk in the remaining enchilada sauce ingredients until smooth and combined.
Turn the heat to low and let simmer 5-8 minutes, until the sauce has thickened.
When the beef and peppers have cooked, remove from the pan and transfer to a bowl.
Spread each tortilla with refried beans, then stuff the tortillas with cooked beef, peppers, and onions.
Wrap the tortillas and place them, seam side down, in a 9x13” casserole dish.
Pour over enchilada sauce and top with shredded cheese.
Place pan in oven and bake 12-15 minutes, until the cheese has melted and it starting to brown.