Preheat the oven to 350°F/175°C, and grease an 8-inch loaf pan and line it with baking parchment paper.
Add the softened butter and sugar to a mixing bowl and beat with an electric mixer until smooth and fluffy (approx 4 minutes).
Beat in the eggs, one at a time, then beat in the wine and vanilla (it may ‘split’ a little, but will come together with the flour).
Sift in the flour, baking powder and salt and mix on low or by hand, until just combined (don’t overbeat it).
Spoon the batter into the prepared pan and spread evenly to the edges.
Bake for 45 to 55 minutes or until a toothpick or knife inserted into the center of the white wine cake comes out clean.
Cool in its pan for 10 minutes, then remove from the pan and cool on a wire rack.
For the glaze, mix the wine and sugar together to get a thick but runny paste (add a little more wine or sugar if necessary to get the right consistency). Drizzle over the completely cooled cake. Slice and serve!
Notes
Don’t overmix once the flour is in.
Room temperature ingredients make a smoother batter.
If your batter splits after adding wine, don’t panic. It comes back together when you add the flour.
Check for doneness with a skewer — it should come out clean.
Let it cool completely before glazing to avoid melting the icing.