In a medium skillet over medium-high heat, cook the bacon until crispy, about 3 to 4 minutes on each side. Remove from the skillet and drain on paper towels.
In a small bowl, combine the mayonnaise, lemon zest, lemon juice, and fresh dill. Spread the lemon mayonnaise over 1 side of each slice of bread. Arrange the smoked salmon on 4 slices of the bread. Break the bacon in half and put on top of the smoked salmon. Top the bacon with 1/2 cup of arugula and arrange 2 to 3 tomato slices on top of the arugula. Cover with remaining slices of bread, lemon mayonnaise side down.
Arrange the sandwiches on a platter and serve.