Cook the peas in lightly salted boiling water for 3 to 5 minutes or until tender.
Meanwhile, in a saucepan heat butter, and add the onion, and saute until tender and golden, about 2 minutes. Remove and drain the peas.
Place the hot, blanched peas into the pan with the onions. Toss in the dill, season with salt and pepper, to taste, with salt and pepper. Toss in the walnuts, and serve.