In large frying pan or cast-iron skillet, cook bacon until crispy. Remove slices from skillet to drain on paper towel. Pour bacon fat from pan.
Shape ground beef into four burger patties, seasoning both sides of patties with salt and pepper.
In skillet over medium-high heat, cook burgers about 4 minutes per side for medium doneness.
Top each burger with one slice cheese then cover skillet with lid and cook until cheese melts. Remove from heat.
In smaller skillet, heat canola oil until hot but not smoking. Quickly crisp tortillas in oil, turning once and removing from pan within 1 minute. Drain on paper towels to remove excess oil.
To build each taco, slice or crumble burgers and cooked bacon. Top each tortilla with 1/2 burger, bacon, onion, avocado, tomato and lettuce. Serve with pickles, ketchup, mustard and mayonnaise, if desired.
