Preheat oven to 400 F. Line a baking sheet with parchment.
Combine flour, 1/2 tsp salt, egg and 2 Tbsp olive oil in a bowl until combined. Pat dough into a 4 inch disk; cover with plastic wrap and chill 30 minutes.
Heat remaining oil in a large skillet over medium heat. Add onion and remaining salt to pan; sauté 3 minutes or until softened and beginning to brown. Add spinach: sauté 1 minute or until wilted. Remove pan from heat and stir in lemon juice. Cool to room temperature.
Unwrap chilled dough and place on prepared pan. Cover top of dough with plastic wrap and roll to a 10 inch circle. Add spinach mixture to crust, leaving a 1 inch border. Sprinkle feta over filling. Using the parchment as an aid, fold edges of dough over filling. Bake at 400 F for 18 minutes or until crust is browned. Cool on parchment, on rack, 10 minutes before slicing. Sprinkle with pepper and pine nuts before serving, if desired.