Add all ingredients to a small mixing bowl and stir to combine. Cover and refrigerate until ready to use.
For the bowl:
Heat oven to 400ºF (200ºC). Arrange the sweet potatoes on a sheet pan and drizzle with olive oil. Season with salt and cook until crispy, tossing half way through cooking, about 20 minutes.
Heat a large cast-iron pan over medium heat, add the oil to the pan and heat through. Add the ground beef and ¼ cup (30g) of the onion and cook, stirring occasionally and using a wooden spoon to break up the meat, until the beef is browned, about 6 minutes. Sprinkle with the Worcestershire sauce and season to taste with salt and pepper. Set aside until ready to serve.
Divide lettuce among serving bowls. Top each with sweet potato fries, ground beef, tomatoes and avocado. Drizzle the sauce over the top, followed by adding the red onion and pickles. Serve immediately.
Notes
To turn the hamburger bowl into a cheeseburger bowl, add a sprinkle of your favorite shredded cheese like Cheddar, Monterey Jack or pepper jack.
Swap the base of the bowl for another green like baby spinach or green leaf lettuce.