Preheat your oven to 350°F (175°C) and grease a 9-inch cake pan. Wash and chop fresh rhubarb into ½ inch pieces and toast pecans for 5 minutes.

In a large mixing bowl, whisk together all-purpose flour, baking powder, ground cinnamon, and salt until well combined.

In another bowl, beat softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes.

Add eggs, one at a time, into the butter and sugar mixture, mixing well after each addition, then stir in vanilla extract.

Gradually add the dry mixture to the butter mixture, alternating with milk or buttermilk until just combined.

Fold in the chopped rhubarb and toasted pecans gently, taking care not to overmix.

Pour the batter into the prepared cake pan and bake for 45-55 minutes or until a toothpick comes out clean.

Allow to cool in the pan for about 10 minutes before transferring to a wire rack to cool completely.