Preheat oven to 350ºF.
Heat olive oil in a large skillet over medium-high heat. Add the onions and jalapeño. Saute for 5 minutes, stirring occasionally, until softened and translucent.
Add the ground beef, garlic, and salt. Use a wooden spoon to break up the meat into smaller chunks. Cook, stirring occasionally, for 6 to 8 minutes, until beef is browned.
Add ¼ cup enchilada sauce, stir to combine, and remove from heat. Taste and season with more salt if necessary.
Microwave the tortillas on a plate for 1 minute, flipping them halfway through until all of them are warm and pliable.
Pour ¼ cup of the enchilada sauce into a 9x13 baking dish, and spread it out to fully coat the bottom.
Assemble the enchiladas by filling each tortilla evenly with the beef mixture and ¾ cup of shredded cheese. Roll the tortillas tightly to close and place in a large baking dish seam side down.
Pour the remaining 1 ¼ cups enchilada sauce over the tortillas, top with the remaining 1 ¼ cups shredded cheese, and bake for 20 minutes, until the cheese is melted and bubbly.
Serve immediately and garnish with desired toppings.
