Bring a large pot of water to a boil and add 1/2 tablespoon salt, then cook the tortellini according to package instructions until al dente.
While the pasta cooks, heat the olive oil in a skillet over medium heat.
Add the minced garlic and baby tomatoes to the skillet and sauté for about 1 minute.
Stir in the lemon zest and half of the minced fresh herbs and cook for another minute.
Reserve 1 cup of the pasta cooking water, then drain the tortellini.
Add the drained tortellini to the skillet and pour in 1/4 cup of the reserved pasta water; lower the heat to a gentle simmer.
Season with a pinch of salt and pepper, add about half of the crumbled feta, and gently toss to combine; add more pasta water, 1/4 cup at a time, if the pasta seems dry.
When the sauce has thickened and the pasta is fully cooked (about 1–3 minutes), remove from heat.
Finish by sprinkling the remaining fresh herbs, the juice of half a lemon, and the remaining feta on top, then serve immediately.