Preheat your oven to 350°F (175°C) and prepare an 8-inch springform pan by greasing and lining it with parchment paper.

In a large mixing bowl, combine eggs and sugar, then beat them together until light, fluffy, and pale in color, roughly 5-7 minutes.

Sift together all-purpose flour and baking powder into a separate bowl. Fold this mixture into the egg and sugar combination gradually.

Stir in the softened butter until the mixture is just combined, resulting in a smooth batter.

Chop the whole orange into quarters and blend it in a food processor until almost pureed. Fold this blend into the batter.

Pour the batter into the prepared springform pan, smoothing the top, and bake for 50-60 minutes until golden brown.

After baking, let the cake cool in the pan for about 15 minutes, then loosen the edges and remove it from the pan.

Make the glaze by combining orange juice and sugar in a saucepan, simmer over medium heat, then brush it over the warm cake.

Let the cake cool completely before slicing for best texture and flavor.