Bake French fries according to package directions; season with a pinch of salt.
Meanwhile, in a small bowl, stir mayonnaise, ketchup, relish, and mustard until smooth.
In a large skillet over medium heat, heat oil until shimmering. Add beef, Cajun seasoning, and ¾ teaspoon salt. Cook, breaking up beef with a wooden spoon, until cooked through and no longer pink, 5 to 6 minutes. Gather beef to one side of skillet in an even layer and top with cheese. Cover with a lid or foil and let melt, 3 to 4 minutes.
Divide lettuce among wide, shallow bowls. Top with cheesy ground beef, bacon (if using), tomatoes, onion, pickles, fries, burger sauce, and sesame seeds.
