Prepare the Filling: In a large skillet, heat a little oil over medium heat. Sauté the chopped onion and minced garlic until softened. Add the chopped spinach and cook until wilted. Remove from heat and allow to cool slightly.

Mix the Filling: In a large bowl, combine the cooked spinach mixture with crumbled feta, ricotta cheese, beaten eggs, dill, salt, and pepper. Mix until well combined.

Assemble the Spanakopita: Preheat the oven to 375°F (190°C). On a clean surface, lay out one sheet of phyllo dough and brush it lightly with melted butter or olive oil. Layer another sheet on top and repeat the brushing. Place a portion of the spinach filling along one edge, then fold the sides in and roll it up tightly to form a log. Place seam-side down on a baking sheet.

Bake: Repeat the process with the remaining phyllo sheets and filling. Brush the tops of the rolls with more melted butter. Bake in the preheated oven for 25-30 minutes, or until golden brown and crisp.

Serve: Let the spanakopita cool for a few minutes before slicing. Serve warm or at room temperature.