Heat two tablespoons of olive oil in a skillet and toast the sourdough cubes until golden brown; remove and sprinkle with a pinch of sea salt.
In a medium bowl, whisk together the Greek yogurt, lemon juice, grated garlic, and half of the Parmesan cheese until smooth to create the dressing.
In a large bowl, toss the chopped romaine lettuce with half of the prepared dressing until well coated.
Pat the salmon fillets completely dry with paper towels to ensure crispy skin.
Season both sides of the salmon fillets generously with kosher salt and cracked black pepper.
Heat the remaining olive oil in a skillet over medium-high heat and sear the salmon skin-side down for 4-5 minutes until crispy, then flip and cook for another 3 minutes until cooked through.
Divide the dressed romaine between four plates, top with a salmon fillet, sprinkle with remaining Parmesan and the prepared sourdough croutons, and drizzle with remaining dressing.