Cook bacon in a skillet over medium heat until crispy, about 6-8 minutes. Transfer to a paper towel-lined plate to absorb excess grease.

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

In a mixing bowl, whisk together mayonnaise, red wine vinegar, salt, oregano, Italian seasoning, garlic powder, and red pepper flakes until smooth.

Add cooled tortellini to the bowl with dressing, then toss in bacon, pepperoncini, tomatoes, and onion. Mix gently to coat.

Cover salad and refrigerate for at least 1 hour, preferably 2 hours, to allow flavors to meld.