Step 1

Preheat the oven to 375 degrees F (190 degrees C). Line a baking sheet with parchment paper.

Step 2

Add sausage to a large skillet over medium-high heat. Cook and stir with a spatula, breaking apart the sausage until cooked, 5 to 7 minutes. Reduce heat to medium. Add spinach, green onions, and red pepper flakes. Continue cooking until the spinach is thawed, 3 to 5 minutes.

Step 3

Remove from heat and stir in ricotta cheese and feta cheese. Season with salt and pepper.

Step 4

Unwrap the phyllo dough and cover with a towel to keep it from drying out.

Step 5

Working with one sheet at a time, brush 1/2 of the sheet with melted butter. Fold it in half lengthwise. Place a 1/4 to 1/2 cup of filling in the top-left corner. Fold the bottom-left corner over into a triangle shape. Continue folding edge over edge until you reach the end of the dough and a triangle shape is formed. Place the triangle on the baking sheet. Repeat with the remaining ingredients.

Step 6

Brush all the triangles with melted butter.

Step 7

Bake in the preheated oven until golden brown, about 25 minutes.