Preheat the oven to 375°F (190°C).
Sauté the onion in olive oil until translucent.
Add garlic and sauté for another minute.
Stir in the spinach and cook until wilted.
Remove from heat and mix in feta, dill, salt, and pepper.
Prepare phyllo dough by brushing sheets with olive oil.
Place some filling at one end and fold into a triangle.
Continue folding until the end of the phyllo sheet.
Place triangles on a baking sheet lined with parchment paper.
Brush the tops with olive oil before baking.
Bake for 25-30 minutes or until golden brown.