Cream Cheese Spread: In a small bowl beat together cream cheese, lemon juice, lemon zest and dill pickles.
Onion Relish: Heat 3 tablespoons olive oil in large sauté pan over medium heat and add sliced onions, sprinkle with salt and pepper. Cover, stirring occasionally for about 10 minutes until onion is softened, tender and slightly browned. Stir in dried blueberries and set heat to low, replace lid and continue cooking for 5 minutes. Turn off heat, stir in fresh or frozen thawed blueberries, cover to keep warm.
Sandwich Assembly: Heat grill pan over medium heat. Brush one side of each bread slice with olive oil. Place oil side down on grill pan until browned, about 2 minutes. Remove bread from grill pan and spread toasted side generously with cream cheese mixture. Top with smoked salmon then onion relish and baby spinach. Top with second slice of bread toasted side down. Brush top with olive oil and place oiled side down on hot grill pan until toasted and nicely browned, about 2 minutes. Brush unoiled top with olive oil and carefully flip over to toast until golden brown, another 2-3 minutes. Cool slightly before cutting in half.