Heat oil over medium-high heat in a Dutch oven. Add ground beef, onion, and jalapeno. Cook, breaking ground beef apart with a wooden spoon, until beef is no longer pink.
Sprinkle taco seasoning over ground beef. Stir to combine.
Transfer ground beef mixture to a bowl and set aside.
Add butter to same Dutch oven and place over medium heat. Once butter is melted, sprinkle flour over butter and whisk together for 1 minute.
Gradually whisk in milk. Add can of Rotel. Simmer until mixture thickens slightly, about 3 to 5 minutes.
Set aside 1/2 cup of Pepper Jack cheese and 1/2 cup cheddar cheese. Add remaining cheese to Dutch oven and remove pan from heat. Stir until cheese is melted.
Add meat mixture and stir to combine.
Add cooked macaroni and stir to combine.
Pour into a greased 11X8-inch pan. (A 13x9-inch will work too.)
Sprinkle the cheese that was set aside and the Doritos on top.
Place in a 350 degree oven and bake for 20 to 25 minutes.
Sprinkle with cilantro.