Preheat oven to 350 F degrees. Line a baking sheet with parchment paper or silicone mat.
Add the pecans to the baking sheet and roast at 350 F degrees for 7-8 minutes until fragrant.
Remove from oven and let them cool down a bit.
Add the toasted pecans to your blender along with cinnamon. Pulse on medium to high speed, the nuts will be crumbly at first and then blend to a creamy butter. The time taken for this will depend on your machine. A high speed powerful blender like blendtec or vitamix would take only 1-2 minutes where a food processor might take 10 minutes or more.
Once the mixture is creamy, add in the brown sugar and pulse again for 15 seconds until the sugar is well combined.
Transfer pecan butter into a jar with an airtight lid. Store in the refrigerator for 3-4 weeks.