Step 1

Mix shallot, lemon zest, lemon juice, and vinegar in a large bowl. Let sit 10 minutes, then mix in oil. Set vinaigrette aside.

Step 2

Meanwhile, mix a palmful of salt into a medium bowl of ice water; add peas. Let sit 10 minutes, then drain and pat dry (this makes them super crisp).

Step 3

Add peas, radishes, cucumbers, romaine, and radicchio to bowl with reserved vinaigrette; toss well to coat. Add feta and dill, season with salt and pepper, and toss again to combine. Transfer to a platter to serve.

Step 4

Do Ahead: Vinaigrette can be made 6 hours ahead. Cover and chill. Bring to room temperature before using.