Take all the ingredients for the cake out of the fridge and let them come up to room temperature for about 30 minutes.
Heat the oven to 180°C/350°F/Gas Mark 4. I use fan assisted.
Grease your bundt pan liberally. I like to use an oil based spray, but if you can get a baking spray with flour that works great too.
Using a sieve sprinkle the pan with lots of flour. It's important that the pan is properly coated for it to release the cake without problems.
Turn the pan upside down and tap it to remove excess flour.
Making the batter
Add sugar and butter in cubes to the bowl of your stand mixer.
Using the whisk attachment, cream the butter until pale and fluffy.
While the mixer is running on medium speed add the eggs on by one, pausing to make sure each is incorporated before adding the next.
Stop the mixer and sprinkle baking powder and fine salt over the top of the dough. Run the mixer to combine.
Then add ⅓ of the flour. Mix until combined. 10-15 seconds.
Add ½ of the milk. Mix until combined.
Add another ⅓ of the flour. Mix until combined.
Add the last of the milk. Mix until combined.
Add the last of the flour. Mix until combined.
Dollop the batter into the bundt pan. Try to get it in as evenly as possible. Use a wet spatula to even the top.
Bake for 40-45 minutes until golden brown and a toothpick comes out cleanly. Make sure you stick the toothpick in somewhere where the top of the dough is cracked so the crust of the dough doesn't scrape off batter that might stick to the toothpick.
Remove from the oven and let cool on a write rack for 15 minutes.
Put the wire rack on top of the pan and invert it and let the cake come out naturally. Cool completely before proceeding.
Preparing the cake for the filling
Soften your gelatin sheet in a lot of water. If you are using powdered gelatin dissolve ⅓ tsp into 1 tbsp of water. Leave to bloom for 10 minutes.
Using a paring knife, you need to make a cavity in the cake. Cut near the outer perimeter of the cake with the knife slanting inwards at about a 45° angle. Then cut the inner perimeter with the knife slanting outwards at a 45° angle. See the video for details.
Remove the cake from the cavity with your fingers. If any of it slips into your mouth at this point, that's totally acceptable ;)
Then use a tablespoon to make the cavity rounded. Make sure you tap out excess crumbs when you are finished.
Making the filling
In a heat proof bowl combine egg whites, powdered sugar and lemon juice.
Put the bowl over a pot of simmering water. The water should not be touching the bowl.
While whisking, heat the mixture to 79°C/174°F.
Once it hits the temperature, take it off the heat.
Wring out your gelatin sheet and add to the warm mixture. Stir until completely dissolved.
Add the mixture to the bowl of your stand mixer.
Using the whisk attachment, turn the speed up gradually until whisking at full speed.
Whisk until you have stiff peaks (10-15 minutes)
Add the meringue to a piping bag, close it at the top and cut a generous hole.
Add the filling to the cake.
Put a cake cardboard over the top of the cake and invert it onto the serving platter or cake stand
Dust the cake with powdered sugar using a sieve, where you tap it lightly on the side to make a beautiful coating.