1/4 cup plus 2 tablespoons pesto, at room temperature
1 tablespoon fresh lemon juice
Salt and freshly ground black pepper
1/4 cup salted, roasted almonds, coarsely chopped
Bring a large pot of salted water to a boil. Add the asparagus and blanch until barely tender, about 4 minutes. Using tongs, transfer the asparagus to a work surface and cut into 1-inch lengths.
Add the tortellini to the boiling water and cook until al dente, reserving 1 tablespoon of the cooking water. Drain the tortellini.
Return the tortellini to the pot. Add the asparagus, butter, pesto, pasta cooking water and lemon juice, season with salt and pepper and toss to coat. Transfer the tortellini to bowls, top with the almonds and serve right away.