The deep purple of the cabbage slaw would be enough to liven up these salmon sliders, but we add even more color with a simple carrot and cucumber side salad.
To prepare slaw: Whisk mustard, oil, vinegar, honey, and 1/4 tsp. pepper in a medium bowl. Add cabbage and fennel; toss to coat. Set aside.
To prepare salad: Whisk yogurt, lemon juice, dill, salt, and 1/8 tsp. pepper in another medium bowl. Add carrots and cucumber; toss to combine. Set aside.
To prepare salmon: Pat salmon dry with paper towels. Season with salt and pepper. If the fillet is too large to fit in the pan, cut it in half. Heat oil in a large cast-iron or nonstick skillet over medium-high heat. Add the salmon, skin-side up, and cook for 4 minutes. Flip and cook until the salmon flakes with a fork, 5 to 6 minutes, depending on thickness.
Divide the salmon among buns (or rolls) and top with the reserved slaw. Serve the salad on the side.
Tip: If you can't find 8 slider buns or small dinner rolls (about 2 inches in diameter), substitute 4 whole-wheat sandwich rolls.