In a large pot, bring 4 quarts of water and 1 tablespoon salt to a boil. Add pasta and cook until soft, not al dente, about 12 minutes. Drain well, rinse with cold water, and drain again.
Meanwhile, in a medium bowl, combine tuna, mayonnaise, celery, onion, relish, lemon juice, and garlic. Season to taste with salt and pepper (I like 1/2 teaspoons salt and 1/4 teaspoon pepper).
In a large bowl, add cooled noodles, tuna salad, and peas, and stir to combine. Chill until serving time.
Notes
Macaroni: Or substitute another small pasta shape. It's important to overcook the noodles so they are soft, not al dente, or they will be too chewy in the final salad once chilled.
Tuna: I prefer tuna packed in water with a dolphin-safe label. Or, substitute oil-packed tuna (feel free to decrease the amount of mayonnaise if you do).
Mayonnaise: This recipe is heavy on the mayonnaise. Start with 1/4 cup if you prefer and add more to taste.
Relish: Or substitute dill relish or minced dill pickles if you prefer that flavor.
Yield: This recipe makes at least 8 cups of tuna pasta salad, enough for 8 servings, 1 cup each.
Storage: Store leftovers covered in the refrigerator for up to 4 days. Some separation may occur, so stir the pasta salad before enjoying again.