In a saucepan, combine water and sugar. Bring to a simmer over medium heat, stirring until sugar dissolves.

Add the orange and lemon zest and juice. Simmer for 15-20 minutes until the citrus is tender and syrupy.

Remove from heat and let cool. Strain the citrus and reserve the syrup.

Preheat the oven to 350°F (175°C). Grease and line a 9-inch round cake pan with parchment paper.

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, alternating with buttermilk, starting and ending with the flour mixture.

Fold in the candied citrus pieces.

Pour the batter into the prepared cake pan and smooth the top.

Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Drizzle the reserved citrus syrup over the cooled cake before serving.

Slice and enjoy your candied citrus cake!