2 tablespoons Mexican hot sauce (like Cholula or Tapatio)
sliced pepperjack cheese
lots of sliced jalapenos
Thoroughly mix ground beef with the taco seasoning and hot sauce in a large bowl. Form into 9 to 12 patties. Grill for 20 or so minutes, flipping once and applying cheese after 10 minutes. Take a bun, and add one layer of jalapenos. Apply mayonnaise, so that it flows into the gaps between and inside the jalapenos (so it won't squirt out when you eat it). Apply 1 cooked patty, and pile on as many jalapenos as you can stomach, and, if desired, add more hot sauce and mayo. Eat.
I had an idea for this recipe over a year ago, but it took two or three iterations to get just right. When I did, it tasted exactly the way I wanted it. To me, this is what a southwestern burger should be, and I will be dissatisfied with other substitutes.