Arrange oven rack to center of your oven and preheat the oven to 350F (175C). Thoroughly grease (I use vegetable shortening) and flour a 12-cup bundt pan or 10" tube pan (see notes to bake in loaf pans). Be sure to tap/shake out excess flour or, rather than greasing/flouring you may spray with baking spray.
In the bowl of a stand mixer (or using an electric mixer), beat together butter, cream cheese, sugar and lemon zest on medium-speed until creamy, well-combined and batter is lightened in color.
Add eggs, one at a time, stirring well after each addition. Scrape the sides and bottom of the bowl and stir in vanilla extract and lemon extract (if using). The mixture should be very smooth, light, and creamy when finished.
In a separate bowl, whisk together flour, baking powder, and salt.
With mixer on low-speed, alternate adding the flour mixture and buttermilk to the butter batter, starting and ending with the flour mixture (I add the flour in 3 parts and the buttermilk in 2).
Pour lemon pound cake batter into your prepared bundt pan and bake on 350F (175C) for 50-60 minutes or until a wooden skewer inserted in the thickest part of the cake comes out clean or (preferably) with a few moist crumbs. If you have a lighter-colored bundt pan, it may take longer in the oven.
Allow to cool for 15-25 minutes and then carefully (it will still be hot! invert onto cooling rack to cool completely before decorating with glaze.
Prepare glaze by whisking together powdered sugar, melted butter, and vanilla extract. Mixture will be very thick until you add the lemon juice.
Add lemon juice, one tablespoon at a time, until the consistency is thin enough that it falls in ribbons off of your whisk, but thick enough that it holds its shape for several seconds before dissolving back into the bowl.
Drizzle lemon glaze over cooled pound cake. Allow glaze to set for 30-60 minutes (this may be faster or longer, depending on the precise thickness of your glaze) and then dig in!
This is optional and I do not use it, but it will give your pound cake a more intense lemon flavor.
This recipe may be baked in two loaf pans instead. Divide the batter evenly into two pans that have been thoroughly greased and floured (or sprayed with baking spray) and bake in the center rack for approximately 50 minutes or until a wooden skewer inserted in the center of the cake comes out clean or with a few moist crumbs.
Store at room temperature in an airtight container or wrapped in plastic wrap or foil for up to five days. While I don't recommend refrigerating this cake (the fridge will dry it out), it may be wrapped tightly and frozen for several months.