Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper. Finely grate the zest from the lemon and cut the zested lemon into quarters.
In a medium skillet, melt the butter over medium. Add the panko and cook, stirring occasionally, until lightly browned, about 3 minutes. Transfer to a small bowl and stir in the lemon zest and 2 teaspoons of parsley. Season with salt and pepper.
In a small bowl, combine the mayonnaise, capers, and garlic. Squeeze lemon juice from one of the lemon quarters into the same bowl. Season with salt and pepper.
Pat the salmon dry and season all over with salt and pepper. Spread the caper mayo on top of each filet and top with the panko, using your fingers to help the panko stick.
Transfer to the oven and bake for 15-20 minutes, until the salmon is about 135°F on an instant-read thermometer and the panko is crispy.
Sprinkle the salmon with a little more parsley and serve with lemon wedges. I like to serve with rice and sometimes a salad.