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, 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. Let cool.

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

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

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

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

Let cool slightly before serving.