In a large skillet, cook the bacon over medium heat until crispy, about 8-10 minutes. Use a slotted spoon to transfer to a paper towel-lined plate to drain excess grease. Cool and chop into bite-sized pieces.

Bring a large pot of salted water to a boil. Add the frozen cheese tortellini and cook according to package instructions, usually around 3-5 minutes, until al dente. Drain and rinse with cold water to cool.

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

Add the cooked tortellini, chopped pepperoncini, half of the Parmesan cheese, chopped red onion, and diced tomatoes to the bowl with the dressing. Toss gently until evenly coated.

Cover with plastic wrap or transfer to an airtight container. Refrigerate for at least 2 hours to chill and allow flavors to meld.

Before serving, stir gently to redistribute dressing. Adjust seasoning if needed. Serve chilled or at room temperature, garnished with remaining Parmesan cheese.