Place the butter in a saucepan and melt over medium heat until it has a nice golden color and a subtle nutty smell. The butter will melt and bubble initially, but keep stirring with a wooden spoon until it reaches the desired color. There's a fine line between noisette butter and burnt butter, so keep a constant eye on it and stir constantly. For me it all took 5-6 minutes. After caramelizing the butter, let it cool to room temperature.
Preheat the oven to 180°C/356° F, no fan.
Grease a cake/bundt pan with butter and dust it with flour!
Put the eggs and sugar in a bowl and beat until light and airy.
Add the vanilla essence and lemon zest (optional), then the flour mixed with baking powder, and mix.
Finally, add the caramelized butter and whisk until smooth.
Pour the mixture into the baking pan and bake 60 minutes. When the cake is ready, a toothpick inserted in the middle will come out clean.
Let the cake cool in the pan for 5 minutes, then flip it over onto a rack and let it cool completely.
Dust the cake with sugar and serve with coffee or tea. It's something else!