Cover 1 egg with cold water in a pot; bring to a boil. Remove from heat; cover; let sit 12 minutes. Run under cold water. Peel and chop egg.
Preheat oven to 325ºF. Warm oil in a skillet over medium-high heat. Sauté onion 4 minutes. Add garlic, paprika, salt and crushed red pepper; sauté 1 minute.
Add spinach to skillet by the handful, stirring after each. Increase heat to high. Sauté 5 minutes. Transfer to a bowl; let cool. Stir in tuna, olives, lemon juice and chopped egg.
Line two baking sheets with parchment. Roll one sheet of pastry on a floured surface to 1/8-inch thickness. Cut out 12 3-inch rounds. Repeat with second pastry sheet. Spoon 1/2 Tbsp. of tuna mixture in center of each round. Fold pastry over; press and crimp edges. Transfer to baking sheets.
Whisk remaining egg with 1 tsp. water. Brush each empanada with egg wash. Bake until deep golden brown, about 35 minutes. Transfer to a wire rack and let cool 10 minutes.