In a small bowl, mix yeast, warm water, and sugar. Let sit for 5–10 minutes until foamy.

In a large bowl, combine flour and salt. Add yeast mixture and olive oil. Knead into a smooth dough for about 8–10 minutes. Cover and let rise for 1 hour.

Meanwhile, heat olive oil in a pan over medium-low heat. Add onions and cook, stirring occasionally, for 15–20 minutes until golden and caramelized.

Add garlic, spinach, oregano, and red pepper flakes. Cook for 2–3 more minutes until spinach is wilted. Season with salt and pepper, then let cool.

Preheat oven to 375°F (190°C) and grease a baking dish.

Roll out the dough into a rectangle on a floured surface. Spread marinara evenly over the dough, then top with the spinach-onion mixture.

Roll the dough tightly from the long side into a log, slice into 10–12 rolls, and place them in the baking dish.

Sprinkle with nutritional yeast if using. Bake for 25–30 minutes until puffed and golden.

Let cool slightly before serving.