Combine balsamic vinegar, olive oil (1/3 cup and 1 tbsp), Italian seasoning, smashed garlic, and salt and pepper in a blender and blend until smooth.
Alternatively use an immersion blender or mince garlic, whisk vinegar and seasoning, then slowly drizzle in oil to emulsify.
Salad
Boil the tortellini according to package instructions (about 2-3 minutes), drain, add to a large bowl, and drizzle with a little olive oil to prevent sticking.
Chop the pepperoni into quarters and add to the bowl.
Add chopped mozzarella, chopped Parmesan, chopped green onions, halved cherry tomatoes, black olives (halved if desired), artichoke hearts, and pepperoncini to the bowl.
Drizzle the blended dressing over the salad and toss to combine.
Serve immediately or refrigerate for a few hours; can be made up to 24 hours ahead and tossed again before serving.
Tips
Slice cheeses into 1/2-inch cubes and halve cherry tomatoes before assembling the salad.
Boil tortellini just 2–3 minutes until tender, then drain and toss with a little oil to stop stickin
Make the salad a few hours ahead and chill; toss again just before serving for best flavor.