Preheat the oven to 200C (400F).
Pierce the sweet potatoes several times with a fork and place them on a baking sheet.
Roast the sweet potatoes for 35-40 minutes until soft and cooked through.
While the sweet potatoes roast, heat a pan over medium heat and add a splash of oil.
Sauté the diced onion until translucent.
Add the sliced mushrooms and crushed garlic to the pan, cooking until mushrooms are soft and golden.
Add the spinach and cook until wilted.
Remove the pan from heat and stir in tahini, nutritional yeast, lemon juice, salt, pepper, and cayenne pepper if using.
Slice the roasted sweet potatoes lengthwise and gently fluff the insides with a fork.
Fill the sweet potatoes with the mushroom and spinach mixture.
Serve warm and enjoy!