Place a large skillet on medium heat and add one tablespoon of oil to warm it up. First, add the chopped onion and diced green bell pepper and sauté until they soften, about 3-4 minutes.
Next, stir in the minced garlic and cook for another minute until fragrant.
Then, add the lean ground beef (or turkey) and cook until browned and crumbly, stirring frequently for about 7-8 minutes. Meanwhile, drain any excess fat.
After the meat is cooked, mix in the diced tomatoes and chopped pickles. In a separate small bowl, combine ketchup, mustard, vinegar, and mayonnaise if using.
Pour the sauce mixture into the skillet and stir well to combine. Season with salt and pepper to taste, and let the mixture simmer on low heat for 5-7 minutes so that the flavors meld together.
Meanwhile, if you are using turkey bacon, cook it in a separate pan until it is crispy.
Finally, spoon a generous amount of the meat mixture onto each toasted bun. Optionally, top with a slice of turkey bacon and extra pickles as garnish.
Serve immediately and savor every bite of these innovative big mac sloppy joes.