Bring a large pot of salted water to a boil over high; add tortellini, and cook according to package directions for al dente, about 5 minutes. Drain and rinse under cold water; drain and set aside.
Whisk together olive oil, vinegar, garlic, salt, oregano, crushed red pepper, black pepper, sugar, pepperoncini brine, and chopped red onion in a large bowl until well combined.
Fold in cooked tortellini, tomatoes, cucumber, salami, mozzarella, olives, sliced pepperoncini, and sliced red onion until evenly coated.
Fold in spinach and basil. Garnish with additional basil, and serve immediately.
