1. In a large bowl, add the granulated sugar and lemon zest. Use your hands to massage the zest into the sugar for about 30 seconds. This helps release the oils from the zest into the sugar, amping up the lemon flavor of the muffins once baked.
2. Add the melted butter, vegetable oil, eggs, milk, Greek yogurt, lemon juice and vanilla. Whisk to combine well.
3. In a separate bowl, whisk together the flour, baking powder, baking soda, salt and poppy seeds.
4. Pour the wet ingredients into the bowl with the dry ingredients. Use a large spatula to gently fold the batter together, being careful not to over mix.
5. Cover the bowl with a dish towel and rest at room temperature for 1 hour.
6. After about 45 minutes, preheat the oven to 425°F. Place paper liners in a 12-cup muffin pan, lining every other cavity to leave space around each muffin. This helps the muffins rise more, resulting in tall, perfectly domed muffin tops. Using this method, you’ll bake just 6 muffins per batch, repeating once the first batch is baked. Make sure to increase the oven temperature back to 425°F before baking the second batch. For best results, cool the muffin tin completely between batches or use a second muffin tin.
7. Once the batter is rested, use a large cookie scoop to fill the liners all the way to the top. Be gentle with the batter and do not overwork it as you fill the muffin pan.
8. Note: While the muffins are baking, make the lemon simple syrup. Bake the muffins in the center rack of the oven for 6 to 7 minutes at 425°F. Reduce the heat to 350°F and bake for an additional 7 to 8 minutes. Avoid opening the oven door during baking. At the end of the baking cycle, check the muffins for doneness using a toothpick inserted into the center of the muffins. The toothpick should come out clean or with a few crumbs remaining.
9. Remove the muffins from the oven and cool in the pan for about 5 minutes. Carefully remove the muffins from the pan and set on a wire rack atop a large piece of wax or parchment paper.
10. Brush the tops of the warm muffins with the lemon simple syrup and top with a sprinkle of poppy seeds if desired.
11. Allow the muffins to cool completely before adding the glaze (optional).

For Lemon Simple Syrup

1. In a small saucepan, add the granulated sugar and zest of a lemon. Use your hands to massage the sugar and lemon together for about 20 seconds, releasing the oils from the lemon into the sugar.
2. Add the lemon juice to the sugar and zest mixture. Bring to a boil and then immediately lower the heat to a simmer.
3. Simmer the mixture for about 6 to 8 minutes until thickened slightly. The sugar should be fully dissolved.
4. Strain the simple syrup through a fine mesh strainer into a bowl, removing the pieces of zest from liquid. Set aside until ready to brush onto the tops of the warm muffins.

For Glaze

1. To make the glaze, add all of the ingredients into a small bowl and whisk to combine. Mixture should be smooth and thick, but pourable. If too thin, add more powdered sugar. If too thick, add more milk. Drizzle the glaze over the top of cooled muffins.