If using fresh peas, in a 1-quart casserole combine peas, onion, and 2 tablespoons water.
Cook, covered, on 100% power (high) for 6 to 8 minutes or till peas are tender, stirring once.
If using frozen peas, cook peas and onion according to the pea package microwave directions.
Let the pea mixture stand, covered, while preparing the dill butter.
For dill butter, in a 1-cup measure combine butter or margarine, lemon juice, dillweed, salt, and pepper.
Cook, uncovered, on high for 30 to 40 seconds or till butter is melted.
Drain the pea mixture.
Toss the pea mixture with the dill butter and walnuts.