Mix flour, salt, and baking powder in a bowl and make a well.
Incorporate oil, beaten egg, and water gradually to form a sticky, elastic dough.
Chill the dough in the fridge for 30 to 60 minutes.
Sauté onion and peppers in oil until soft.
Add scallops to the pan and fry for 30 seconds.
Mix in ham, parsley, lemon juice, salt, and pepper, then cool for 20 to 30 minutes.
Preheat oven to 200°C and oil a baking sheet.
Divide pastry into two-fifths and three-fifths portions.
Roll the larger portion into a circle and place on the baking sheet.
Spread filling over the pastry leaving a 2cm border.
Brush the border with beaten egg and top with the remaining rolled pastry.
Crimp the edges to seal and brush the top with egg wash.
Cut small slits in the top and bake for 20 to 25 minutes until golden.