Like all nuts and seeds, walnuts can be toasted on the stovetop, in the oven, or in the microwave. Oven-toasting works particularly well for larger batches of walnuts. Toasting in the microwave typically works best for smaller amounts of 1/2 cup or less, according to the University of Nebraska-Lincoln.
To toast walnuts in the oven, arrange them on a rimmed baking sheet and bake for five to 10 minutes at 350 degrees Fahrenheit. Shake the pan once or twice to promote even browning of the walnuts. The nuts are toasted when they have a golden color, and they continue browning as they cool.
To toast walnuts on the stovetop, place a dry, heavy-bottomed skillet over medium heat. Add the nuts and heat them for approximately one to two minutes, stirring them frequently for even toasting. The nuts are done when they are fragrant and golden.
To toast walnuts in the microwave, spread them in an even layer in a microwave-safe plate or dish. Add approximately 1/2 teaspoon butter or oil for each 1/2 cup walnuts, and stir the nuts to coat them evenly with the fat. Microwave the walnuts for one minute on high. Stir the nuts, and microwave them for an additional minute on high. Continue stirring and cooking the nuts in one minute increments until the walnuts are fragrant and browned.