Preheat the oven to 350°F and prepare the veggies. Slice potatoes into ~½ inch rounds, and then dice them into ½” cubes. Finely dice the white onion, bell pepper, and jalapeño, too.
Add the diced potatoes to the casserole dish and coat in olive oil and salt + pepper. Pop them into the oven for 25 minutes. We’re coming back to them, but potatoes need longer to cook, but in the meantime make the fry sauce and meat mixture next.
For the fry sauce, combine all of the ingredients in a glass measuring cup or small bowl and stir. If you’d like, you can also add little pieces of diced pickle to the sauce for more texture.
Then, heat a skillet to medium heat and grease with cooking spray. Add the lean ground beef, diced bell pepper, onion, and jalapeño. Mix until the ground beef is ~80% cooked, then mix in the Worcestershire sauce and ranch seasoning. Allow the beef to cook through.
By this time, the potatoes should be finished. Remove from the oven but keep the oven on. Add ground beef mixture, canned tomatoes (drained), and ½ of the fry sauce on top of the potatoes. Stir it all together.
Then, top the mixture with pickles, sesame seeds, and cheese and cover the casserole with tinfoil sprayed with cooking spray (tinfoil is a must, otherwise it will significantly dry out). Bake for another 20 minutes.
Serve on a bed of shredded lettuce and add remaining fry sauce. Enjoy!