Form the ground beef into two equal sized 4 ounce patties and season with salt and pepper. Make an indentation in the center of the patty. Place on a hot grill or skillet. Cook for 4-5 minutes on each side, or until it's cooked to the desired temperature.
Also place onion + sweet potato slices on grill or skillet to caramelize. Cook for 2-3 minutes on each side.
Portion out the romaine into 4 servings. Mix together the lemon juice and olive oil, and dress the lettuce. Top with the tomato slices, sweet potato, pickles, and onion.
Let burger patty cool for 5 minutes, then place on top of the burger bowl.
Add ketchup, mustard, or other condiments as desired.