Preheat oven to 400° F. In a stand mixer bowl, combine the flour, sugar, poppy seeds, lemon zest, baking powder, baking soda, and salt. Gently whisk to combine.
Add the cold, cubed butter pieces and using a bowl scraper, cut the butter into the flour until butter is the size of peas. (You don't want to use your hands because our hands are too warm to hold the butter. Cold ingredients make the best scones!)
Place the bowl on the stand mixer and add in the Greek yogurt, cold heavy cream, egg and 1/4 cup lemon juice. Mix on medium speed. The dough will come together and shape into a ball.
Transfer dough to a lightly floured surface and (handling lightly, as you don't want to over-work this dough) Make sure to use flour so the dough does not stick. Fold the dough in half over itself and use your hands to gently flatten layers together.
Gently knead: Rotate the dough 90 degrees and fold in half again, repeating this step 5 times and taking care to not overwork the dough. Use any extra flour as needed. With your hands, shape the dough into a large circle ~1 inch thick. Using a knife, cut in half long ways, and then cut again crossways, and make each section into triangles. It will make 8 scones.
Transfer wedges to a baking sheet lined with parchment paper and place about 2" apart. Brush lightly with heavy cream and sprinkle with sugar. Bake for 16-18 minutes 400°F or until tops are lightly browned. Do not over bake, scones will become dry.
Remove from oven and let cool.