In a small bowl, combine flour, kosher salt, lemon zest, garlic, and sumac, then whisk to combine.
Pat salmon dry on both sides, then place on a plate or tray. Pour flour mixture on top of the fish, then cover with plastic wrap and refrigerate.
Combine olive oil, red wine vinegar, sliced shallots, and sliced serrano pepper in a medium bowl. Whisk, then set aside.
When ready, preheat a large skillet over high heat. Add olive oil. Shake any excess flour off of salmon, then sear flesh side down. Transfer salmon to a bowl or dish with deep sides, then immediately pour the marinade on top.
To serve, pour ½ cup sliced olives and ¼ cup roasted red peppers on top, then garnish with fresh dill. Can be eaten as is or smashed on top of sliced, toasted bread.