In a medium pot, heat over low the milk, cream and lemon rind, until very hot but do not boil. Remove from heat and let cool to warm.
In a medium pot add yolks and sugar, whisk together until combined, then add flour and vanilla and whisk again until smooth, place the pot over medium / low heat, pour the warm milk/cream through a sieve to remove the lemon rind (discard), whisk continuously until thickened. Move to a glass bowl, cover with plastic wrap (make sure wrap touches the cream mixture) and let cool 30 minutes, then cover and refrigerate for about 1½-2 hours.
Pre-heat oven to 350F (180C) Grease and flour a 9 inch (23-24 cm) cake pan (a springform pan if you have it).
LEMON CAKE
In a medium bowl whisk together flour, salt, baking powder and zest, set aside.
In a large bowl on medium speed beat the eggs, yolk and sugar until pale and creamy, approximately 5 minutes, then beat in the milk, vegetable oil and vanilla until combined, then add the whisked flour mixture and combine.
Pour the batter into the prepared cake pan and spoon ¾ of the pastry cream on top of the batter, do not stir. Bake for approximately 40-45 minutes. Check the cake at about 30-35 minutes and if browning on top too much, cover with foil and continue baking until done. Test with a toothpick for doneness. Let cool completely before dusting with powder sugar. Enjoy!
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Notes
To make Cake flour, from 1 cup of all purpose flour remove 2 tablespoons and replace with 2 tablespoon of corn starch, sift to combine.For room temperature eggs and milk, remove from the fridge 30-45 minutes before using.You are going to have some leftover pastry cream, it can be eaten as is or used to fill tart shells.Because there is Pastry cream in the cake it should be stored in the refrigerator. Be sure to eat the cake within 3 days.