Preheat oven to 375° F. Using non-stick cooking spray, generously grease and lightly flour a mini Bundt pan and set aside; I have had the most luck using non-stick cooking spray + flour to release perfect bundt cakes.
Zest both oranges and set aside. Peel the remaining white part and place the orange wedges into a food processor to puree (remove any seeds if there are any). Set aside.
Using an electric stand mixer fitted with the paddle attachement, cream the butter and sugar together for about 3-4 minutes until light and fluffy. Add the eggs, one at a time, waiting until each is fully incorporated. Add the orange puree, zest and vanilla extract and mix until well combined.
In a separate bowl, mix together the flour, baking powder, and salt. While, your mixer is on low, add your flour mixture slowly into the wet ingredients until fully combined. Last, lightly sprinkle your strawberries with a little flour, add the strawberries and gently mix into the batter.
To create the swirl: Pour a little of the cake batter into each prepared mini Bundt well, using a pastry bag or ziplock bag, squeeze the Nutella over the batter in each mini well and swirl into the batter with a butter knife. Then, cover the Nutella with more cake batter, spreading so that it is evenly distributed. Bake for about 20-22 minutes or until a tester inserted in a mini bundt cake comes out clean.
Allow the cake to cool in the pan for about 15-20 minutes before inverting onto a wire rack to cool.
When completely cooled, dust with confectioner's sugar and serve with fresh strawberries if desired.