Cut salmon into large chunks and season with kosher salt. Pulse salmon in a food processor until finely chopped, or grind, or chop finely by hand.
Form the salmon into 3oz balls, or slightly larger than a golf ball.
Heat 1 Tbsp olive oil in a skillet over medium-high heat. Add salmon patties to the hot skillet, pressing them with a flat spatula lined with parchment to "smash."
Cook patties for 1-2 minutes per side until golden brown and cooked through. Toast ciabatta rolls until lightly browned, set aside.
In a small bowl, mix mayo, garlic, capers, lemon zest, and lemon juice to make the lemon caper mayo.
Spread lemon caper mayo on the cut sides of each toasted roll. Place a salmon patty on the bottom half of each roll and top with the other half. Top with tomatoes, arugula and red onion.
Slice in half and crush!
