In a medium to large skillet, heat 1 tablespoon of olive oil. Add the onions and red peppers and saute until they become tender. Set aside.
To make the avocado cream, halve the avocado and remove the pit. Scoop the avocado into a food processor and puree. Add the tomatillo ranch dressing and pure until smooth. Set aside.
In a medium bowl, mix ground chuck and fajita seasoning until well combined. Form into four patties and grill to your desired doneness. Top each cooked patty with a slice of pepper jack cheese.
Place each burger on a bun. Top with lettuce, a scoop of onions and peppers, crispy jalapenos and spread a generous helping of Avocado Cream onto the top bun.
Serve with homemade baked fries or chips and salsa.