Bake flatbread according to package directions. In a food processor, blend cream cheese, 1 cup (250 mL) arugula and lemon juice until smooth. Evenly spread cream cheese mixture on prepared flatbread. Place smoked salmon in a single layer on flatbread, drizzle with honey mustard and top with remaining arugula, dill, green onion, capers and egg. Cut into 16 small squares and sprinkle pepper overtop. Serve immediately.
Leftover slices make a tasty breakfast the next day.