In a large skillet over medium heat, cook the bacon until crispy, roughly 8-10 minutes, stirring occasionally. Transfer the bacon to a paper towel-lined plate to drain excess grease, then chop into bite-sized pieces.

Bring a pot of salted water to a rolling boil and add the frozen cheese tortellini. Cook according to package instructions, usually 3-5 minutes, until al dente. Drain and rinse gently under cold water to stop cooking.

In a large mixing bowl, combine mayonnaise, red wine vinegar, salt, oregano, Italian seasoning, garlic powder, and red pepper flakes (if using). Whisk until smooth and creamy.

Add cooked tortellini, chopped bacon, pepperoncini, Parmesan cheese, diced red onion, and sliced tomatoes to the bowl. Toss gently to coat.

Cover with plastic wrap or transfer to an airtight container, then refrigerate for at least 2 hours.

Before serving, stir gently and add extra Parmesan on top if desired.