Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until al dente. Drain and rinse. Set aside.
In another large pot of boiling salted water, add the asparagus and blanch until bright green and slightly tender, about 3 minutes. Remove with a slotted spoon or a spider and shock in icy cold water. Remove from the water and dry well.
Trim the ends of the asparagus and cut into bite-size pieces on the bias.
Whisk together the mustard, garlic, lemon juice, and olive oil in a small bowl. Season with salt and pepper, to taste.
Combine the reserved asparagus and pasta in a large serving bowl. Add the tomatoes, dill, peas, feta, and the mustard dressing. Toss with tongs to coat the salad well. Taste and add additional salt and pepper, if needed.