Keeping a package of individually-wrapped frozen salmon fillets in your freezer is a handy trick that can redefine the concept of a last-minute dinner. Transfer the fish from the freezer, where it can be safely stored for up to three months, or from the refrigerator, where it can be stored for up to 24 hours, directly to the stove. If you prefer, steam the fish in the packets on a low level for 2 to 3 minutes in the microwave. Recommendations from the Ohio State University Department of Human Nutrition warn against thawing fish at room temperature as well as re-freezing thawed fillets, which can contribute to bacteria development.
Heat 1 tsp. of olive oil in a medium nonstick pan over moderately-low heat. Place the salmon in the pan and cover it with a lid. Depending on the thickness of the fish, cook it for 5 to 10 minutes or until it is warmed through.
Meanwhile, combine 2 tbsp. of Dijon mustard and 2 tsp. of lemon juice in a small bowl until the mixture is creamy.
Drain the excess moisture that collected in the pan from thawing the fish. Return the pan to the stove. Spread half of the mustard mixture over the fillets. Increase the heat to medium and cook, covered, for 5 to 7 additional minutes.
In a medium bowl, combine the remaining half of the mustard mixture with 3/4 cup of mayonnaise, 1/3 cup of diced cucumber, 1/4 cup of diced onion, 1 tsp. of dill weed, 1 minced garlic clove and 1/4 tsp. of red pepper flakes.
Uncover the pan and increase the heat to medium-high. Cook for 1 or 2 minutes or until the fish is just crispy.
Immediately remove the salmon from the pan when finished cooking. Serve the fish with the prepared sauce alongside brown rice, whole-wheat pasta or vegetables.