Preheat the oven to 450F.
Heat a medium cast iron skillet over medium-high heat. Rub pieces of Salmon with 1 Tbsp of oil. While on a plate, salt the skin side. When pan is hot, add remaining 2 Tbsp of oil. Add Salmon fillets, skin side-down. Salt other side of Salmon and cook for for 5 minutes. Flip and cook on the other side for 3 minutes. Remove Salmon from pan and set on a plate, skin side-up.
Turn heat to medium-low. Add Asparagus and Snap Peas to pan and season with Salt and Pepper. Cook, stirring occasionally, until vegetables are cooked through, but still firm, 4-5 minutes.
Remove pan from heat, add Salmon on top of Vegetables, skin side-up and put the skillet into the preheated oven for 2-3 minutes, just to ensure that the Salmon is warm upon serving. Remove from oven and top with Green Onion.
Drizzle with Miso-Ginger Sauce after plating.