Argentinean Beef Empanadas

2 yellow onion, finely chopped

1 green bell pepper, finely chopped

3 garlic, minced

500 g beef

150 g unsalted butter, cold, cubed

2 egg, lightly beaten (for dough)

1 egg, beaten for brushing

500 g all-purpose flour

120 ml water, cold

30 ml vegetable oil

150 g green olives, pitted and sliced

10 ml kosher salt, divided

10 ml cumin

10 ml smoked paprika

5 ml dried oregano

2 ml cayenne pepper

2 ml black pepper, freshly ground