Rhubarb Lavender Streusel Muffins

Name: Rhubarb Lavender Streusel Muffins
Ingredients: Streusel:; 1/4 cup all purpose flour; 2 tablespoons brown sugar; 1 teaspoon lemon zest; pinch of salt; 1 1/2 tablespoons unsalted butter, melted; Muffins:; 1/2 cup granulated sugar; 5 teaspoons dried lavender; 1 cup all-purpose flour; 3/4 cup white whole wheat flour; 1 teaspoon baking powder; 1/2 teaspoon baking soda; 1/4 teaspoon salt; 6 ounces plain Greek yogurt; 2 teaspoons lemon zest; 1 egg; 1 teaspoon vanilla extract; 6 tablespoons unsalted butter, melted; 1-1 1/2 cups diced rhubarb