Preheat oven to 425°F. Roast sweet potato on baking sheet whole until fork tender when pierced with a fork, about 45 minutes.
Meanwhile, heat a small amount of water in a pan and add the onions. Sauté for 5 minutes until the onions soften.
Add the garlic and sauté for 3 minutes until fragrant.
Add mushrooms, bell peppers, and broccoli and cook for 15 minutes until the vegetables are tender.
Turn off the heat and stir in the spinach and ground flaxseed.
Cut the sweet potato in half and light mash with a fork.
Pour sautéd vegetables on top and enjoy!