Line baking sheet with parchment paper. Set aside.

Preheat broiler. Arrangle slices of sourdough on prepared sheet and broil 1-2 minutes on each side until lightly browned.

In a small bowl, whisk mayo, lemon zest, 3 Tbsp. dill and Old Bay seasoning.

In medium bowl, mix together crabmeat, red onion and salt. Add 2 Tbsp. of the mayo mixture to the crabmeat mixture until well combined.

Spread the remainder of the mayo mixture onto the toasts and top each slice evenly with the crabmeat mixture.

Top each toast with a slice of tomato and sprinkle with cheese.

Broil for 3 minutes or until cheese melts. Remove from oven and sprinkle with salt and freshly ground pepper and the remaining dill.

Serve immediately.