Lower the oven rack to the lower third position and preheat the oven to 350°F Line a 9×5 inch loaf pan with parchment paper.
In a large bowl, whisk the flour, baking powder, and salt together. Set aside.
With a handheld or stand mixer fitted with whisk attachment, beat the butter on high speed in a large bowl until smooth for 1 minute. Add the sugar and beat on high speed for 2 minutes. Scrape down the sides and up the bottom of the bowl as needed.
With the mixer running on low speed, add the eggs one at a time. Once the last egg is completely mixed in, stop the mixer. Add the ricotta, lemon juice, lemon zest, lemon curd, oil, and vanilla extract, then beat on medium speed until combined. Scrape down the sides and up the bottom of the bowl as needed.
With the mixer running on low speed, slowly add the dry ingredients just until combined. Do not over-mix.
Spread the batter into prepared loaf pan and bake for 50 minutes. The cake with aluminum foil halfway through baking to prevent the top from over-browning. Baking times vary, so keep an eye on yours and don’t be alarmed if yours is taking longer. The cake is done when a toothpick inserted in the center comes out clean.
Remove the cake from the oven and place on a wire rack. Allow cake to cool in the pan completely before removing from pan.
I prefer to add the icing once the cake has completely cooled. Whisk all of the icing ingredients together and pour over cake. Serve immediately or wait until the icing sets completely, which provides your with clean slices.
Cover and store leftover cake for up to 1 week in the refrigerator.