Lemon Upside-Down Cake

When combined with sugar, the natural pectin in the citrus creates a pudding-like upside-down layer that's similar to a buttery marmalade. Sure, you can make upside-down cake with other fruits, but if you have a backyard lemon tree, this version is the way to go. (If you buy your lemons, be sure to track down fruit with unwaxed peels.)

Lemon Topping:
1 stick butter (113 g)
½ cup + 2 Tbsp. Monk Fruit Sweetener with Erythritol (Granular) (100 g)
2 large unwaxed lemons, ends trimmed, then halved, seeded and sliced to ⅛" thick

Yogurt Cake:
2½ cups all-purpose flour, unbleached (313 g)
1 tsp. baking powder
½ tsp. baking soda
½ tsp. sea salt
2 large eggs
1 cup extra-virgin olive oil (236 mL)
1 cup full fat plain Greek yogurt (227 g)
1 cup Monk Fruit Sweetener with Erythritol (Granular) (200 g)

Preheat the oven to 350°F (180°C/160°C fan, Gas Mark 4). Position a rack in the center of your oven. Butter a 9" round cake pan and line it with parchment paper.

Make the Lemon Topping:
In a medium saucepan over low heat, melt the butter. Remove the pan from the heat and add ½ cup of the sugar and 2 Tbsp. of water. Whisk the mixture until the sugar dissolves and the mixture is glossy and thickened a little. Pour the melted butter and sugar into the prepared cake pan and smooth into an even layer to cover the bottom. Place the cake pan in the freezer until the butter and sugar layer freezes; leave the pan in the freezer until you are ready to transfer the batter to the pan.

In a small bowl, gently toss the lemon slices with the remaining 2 Tbsp. of sugar. Leave the lemon slices in the sugar to macerate for 10 minutes.

Make the Cake Batter:
Sift the flour, baking powder, baking soda and salt into a large bowl. Set aside. Combine the eggs with the olive oil in another large bowl and beat vigorously with a whisk until well combined. Add the yogurt and sugar. Make a well in the flour mixture and add the wet mixture in three additions, folding in each addition until no dry bits of flour remain. Set aside.

Assemble:
Fan the lemon slices out to cover the melted butter and sugar in the cake pan, overlapping the slices by as much as 1⁄8". Pour the cake batter directly on top of the lemon slices.

Bake for about 1 hour, until a cake tester inserted into the center comes out with only a few moist crumbs clinging to it. Transfer to a wire cooling rack and let cool for 15 minutes. Invert the cake onto a serving plate and carefully remove the parchment paper lining. Allow the cake to cool for 1 hour more before serving.

Makes one 9" cake.

Cook's Notes:

• This cake can be made with nearly any citrus, my favourite being lemon because I like it to be bitter and tart.
• The only citrus I would not use is raw grapefruit, oro blanco, or lime. The rinds of grapefruit and oro blanco are much thicker than lemons and oranges and they will take longer to bake.
• Lime and grapefruit also retain too much of the bitter quinine flavour and will make for an odd tasting cake.