In a medium bowl, combine the chopped rhubarb, flour, granulated sugar, baking powder, baking soda, salt, and cinnamon. Mix well to coat the rhubarb with the dry ingredients.

In a separate bowl, whisk together the egg, milk, and vanilla extract until well combined.

Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix; a few lumps are okay.

In a large skillet, heat about 1 inch of vegetable oil over medium heat until it reaches 350°F.

Using a spoon or small ice cream scoop, drop spoonfuls of the batter into the hot oil, being careful not to overcrowd the pan. Fry for about 2-3 minutes on each side, or until golden brown.

Remove the fritters from the oil and place them on a paper towel-lined plate to drain excess oil.

Dust the warm fritters with powdered sugar before serving.