Preheat your oven to 350°F. While it heats, lightly grease a 9-10 inch cast iron skillet or round baking dish with a bit of the olive oil. This prevents sticking and ensures even browning on the bottom of your frittata.

Heat the remaining 1 tablespoon of olive oil in a large skillet over medium-high heat. Add the diced red onion and 1/2 teaspoon of salt, cooking for 5-7 minutes until the onion begins to soften and develop light caramelization. This builds a sweet, savory base for the frittata. Dice your red bell pepper into bite-sized pieces while the onion cooks to save time.

Add the diced red bell pepper to the softened onions and cook for 2 minutes. Stir in your freshly minced garlic and cook for just 30 seconds until fragrant—this prevents the garlic from burning. I always mince garlic fresh rather than using pre-minced because it delivers a sharper, cleaner flavor that really brightens the dish.

Add the spinach to the skillet and stir constantly for 2-3 minutes until completely wilted and any excess moisture has evaporated. Stir in the sun-dried tomatoes and remove the skillet from heat. Let this vegetable mixture cool slightly while you prepare the egg mixture—this prevents the eggs from scrambling when they hit the hot pan.

In a large bowl, whisk together the eggs, almond milk, 3/4 teaspoon of salt, pepper, and nutritional yeast until well combined and slightly frothy. The nutritional yeast adds a subtle umami richness and a hint of cheesy flavor that dairy-free frittatas really benefit from—it rounds out the dish beautifully without being obvious.

Return the sautéed vegetable mixture from Step 4 to the greased baking dish, spreading it into an even layer. Pour the egg custard from Step 5 evenly over the vegetables, gently stirring to distribute the veggies throughout. Transfer to your preheated 350°F oven and bake for 25-30 minutes until the frittata is set around the edges but still slightly jiggly in the very center—it will continue cooking as it cools.

Remove the frittata from the oven and let it rest for 10 minutes before slicing. This resting period allows the residual heat to finish setting the center while the frittata cools enough to hold together cleanly when cut. Slice into wedges and serve warm or at room temperature.