Meanwhile, toss broccoli with the remaining 2 tsp. oil, 1/4 tsp. salt, and 1/8 tsp. pepper in the same bowl. Remove the baking sheet from oven. Stir the sweet potatoes and move them to the sides of the pan. Arrange salmon in the center of the pan and spread the broccoli on either side, among the sweet potatoes. Spread 2 Tbsp. of the mayonnaise mixture over the salmon. Bake until the sweet potatoes are tender and the salmon flakes easily with a fork, about 15 minutes.