Preheat oven to 350 degrees F. Butter and flour the inside of an 8 or 10-cup bundt pan.
In a small bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a standing mixer fitted with the paddle attachment (or a large mixing bowl), place the sugar. Zest the lemon right into the bowl over the sugar (save the fruit for the glaze). With your fingers, rub to combine. The sugar should become lightly moist and fragrant.
Add the butter. Beat on medium-high speed, until pale and fluffy, about 2 minutes.
Scrape down the bowl. On medium speed, beat in the Greek yogurt. Beat in the eggs one at a time, beating after each until fully incorporated. Beat in the vanilla extract.
Reduce the mixer speed to medium-low. Slowly add half of the flour mixture. Once the flour mixture disappears, mix in all of the buttermilk. Mix in the remaining flour mixture, stopping as soon as it disappears.
Pour batter into the prepared bundt pan. Bake for 40 to 50 minutes, just until a toothpick inserted in the center comes out clean. Place the pan on a wire rack and let cool for 10 minutes. Run a butter knife along the outside and center edges of the cake to loosen it, then invert the cake onto a serving plate or cake stand.
While the cake is baking, prepare the glaze: In a liquid measuring cup with a spout, stir together the sugar and lemon juice. Let stand, stirring periodically.
Once the cake has been inverted on the plate but while it is still warm, use a skewer (a toothpick is too short), to poke lots of deep holes all over the exterior of the cake (really go for it!). Pour half of the glaze very slowly over the cake, letting it seep into all the holes. With a pastry brush, brush the glaze that drips down onto the plate all over the cake's sides and top.
Let the cake cool (and the glaze absorb) for 20 minutes. Pour remaining glaze over the cake and let sit at least 10 more minutes, brushing it once more. Just before serving, dust with powdered sugar. Enjoy!
Notes
*Ingredient Note: If you do not have buttermilk, mix 1 1/2 teaspoons white vinegar or lemon juice with 1/2 cup regular milk (use whole milk for the best results, or 2%). Let sit 5 minutes, then use in the recipe as directed.
**Serving-Size Note: For a smaller yield, the recipe can be halved and baked in a 6-cup bundt pan for 30-35 minutes. (I have tried this, and the cake turned out beautifully.)
TO STORE: Store cake in an airtight storage container at room temperature or in the refrigerator for up to 1 week.
TO FREEZE: Freeze cake in an airtight freezer-safe storage container for up to 3 months. Let thaw overnight in the refrigerator before serving.