Preheat your oven to 375°F (190°C).
In a large skillet, heat olive oil over medium heat and add the chopped onion and garlic. Sauté until softened.
Add the fresh spinach to the skillet and cook until wilted. Remove from heat and let cool slightly.
In a bowl, combine the cooled spinach mixture with feta, dill, salt, and pepper, stirring until well incorporated.
Lay one sheet of phyllo dough on a clean surface and brush lightly with olive oil. Layer an additional sheet on top and brush again.
Cut the layered phyllo sheets into three long strips.
Place a tablespoon of the filling at one end of the strip and fold it over to form a triangle. Continue folding to the end of the strip to create a triangle shape.
Place the formed triangles on a baking sheet lined with parchment paper and brush the tops with olive oil.
Bake in the preheated oven for 25-30 minutes or until golden brown and crisp.
Remove from the oven and let cool slightly before serving.
