Mix flour and salt, cut in butter until coarse crumbs form.
Whisk egg, water, vinegar; combine to form dough, knead briefly, chill 30 min.
Sauté onion in oil 3–4 min, add garlic & bell pepper; cook 3 min.
Stir in tomato paste, paprika, cumin 1 min, then add tuna, eggs, olives.
Season, cool completely, mix parsley.
Roll chilled dough into 5–6 inch circles, fill 2–3 tablespoon tuna mixture.
Fold into half-moons, seal edges, crimp with fork.
Brush with egg wash, sprinkle sesame seeds, slit tops.
Bake 25–30 min at 375°F until golden brown; cool 5 min.
Serve warm with salsa verde or tomato sauce.