After brussels sprouts have been trimmed cut larger sprouts lengthwise, while leaving smaller ones whole. Toss in bowl with 2 tablespoons avocado oil and ground cinnamon, using hands to coat if necessary.
Heat a large cast iron skillet over medium heat. Once the pan is hot add remaining avocado oil and coated cinnamon brussels sprouts in single layer.
Cook brussels sprouts on one side, allowing them to sit for 3-4 minutes. Then toss and stir brussels sprouts to cook on other side, another 3-4 minutes.
Lower heat if necessary and cook the brussels sprouts another 6-8 minutes, stirring occasionally, until sides are golden. Remove from heat and cover with lid.
While the cooked brussels sprouts are resting in the pan make the spicy pumpkin aioli: simply mix together pumpkin puree, mayo and sriracha sauce until combined.
Serve brussels sprouts with spicy pumpkin aioli and enjoy as an appetizer or great side dish!