In a large mixing bowl, whisk together the mayo, sour cream, salt, and pepper until smooth and well combined. Stir in the fresh dill, which will infuse the dressing with bright, herbaceous flavor as it sits. This base can be made while the peas thaw, saving you time.

Thaw the frozen peas by running them under cool water in a colander, then drain thoroughly and pat dry with paper towels—excess moisture will dilute your dressing and make the salad watery. While the peas drain, crumble the crisp-cooked bacon into 1/2-inch pieces and finely mince the red onion. Shred or crumble the cheddar cheese into small pieces.

Add the drained peas, crumbled bacon, red onion, and cheddar to the dressing from Step 1. Gently fold everything together until the peas and other ingredients are evenly coated with the creamy dressing. I like to taste as I go and add a little extra salt and pepper if needed—since frozen peas are quite mild, they often benefit from seasoning adjustment. Chill until ready to serve.