Rinse the berries and add to a small bowl, mashing the berries with a fork. Transfer the berries to a fine-mesh strainer sitting over a bowl and using a small soup ladle press the berries to release the juice. You should have about a ⅓ cup of raspberry puree.
Making the Cake
Preheat your oven to 325 degrees
In a large bowl whisk the flour, sugar, baking powder and salt
Separate 5 eggs putting the yolks in a medium-sized bowl and the whites in a stand-mixing bowl or a large bowl. To the egg yolks add 2 whole eggs and whisk to combine. Add the water, vegetable oil, and vanilla to the eggs and whisk until smooth.
Pour the egg yolk mixture into the flour mixture and whisk to make a smooth batter.
Add the raspberry puree to the batter and whisk to combine. Optionally, you can add a few drops of red food coloring to the batter.
Make the meringue by beating the egg whites with a whisk attachment of a stand mixer or use a handheld mixer just until foamy. Slowly add the cream of tartar and whisk the egg whites until they become dry and stiff (beat about 7 - 10 minutes)
Incorporate the egg whites in two batches. Add the first half to lighten the batter and fold into the cake batter using a rubber spatula. You do not have to fully mix in the meringue. Now add the second half of the meringue and slowly fold until no streaks of meringue is visible. Make sure to scrape the bottom of the bowl. Go slowly so you don't deflate the airiness of the batter.
Pour the batter into an ungreased tube pan. Bake for about 55 - 65 minutes or until cooked through.
Remove from oven and invert the cake pan on a wire rack or a bottle to let cool for several hours.
When you are ready to depan the cake, run a knife around the outside edges and the inside tube to release the cake. You may need to run a knife around the flat bottom of the pan. Place the cake on a platter.
Making the Glaze
Mix the powdered sugar, softened butter, 10 raspberries, and lemon juice until smooth.
Spoon the glaze over your cake and let drizzle down the side.