Lemon Poppy Seed Muffins

Name: Lemon Poppy Seed Muffins
Ingredients: 2 tbsp. granulated sugar; 2 tbsp. coarse sanding sugar, divided; 1 tsp. lemon zest; 1/4 c. plus 2 tbsp. all-purpose flour; 1/4 tsp. kosher salt; 2 tbsp. unsalted butter, cold and cubed; 3/4 c. granulated sugar; 1/4 c. lemon zest (from about 4 lemons); 2 1/4 c. all-purpose flour; 2 tsp. baking powder; 1/2 tsp. baking soda; 1/2 tsp. kosher salt; 2 tbsp. poppy seeds; 1/2 c. buttermilk, room temperature; 1/4 c. fresh lemon juice (from about 2 lemons); 1/2 c. unsalted butter, melted; 2 large eggs, room temperature; 1 1/2 tsp. vanilla extract; Yellow gel paste food coloring (optional); 1 c. powdered sugar; 1/2 tsp. vanilla extract; 2 tbsp. fresh lemon juice