Warm the milk gently until hot but not boiling. Add Earl Grey tea bags and crushed lavender. Let steep for 10 minutes. Remove tea bags and strain lavender. Allow milk to cool completely.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large mixing bowl, beat softened butter and sugar until light and fluffy (about 3–4 minutes).
Beat in eggs one at a time. Add vanilla extract and lemon zest. Mix until fully combined.
Gradually add dry ingredients to the butter mixture, alternating with infused milk. Mix until just combined. Do not overmix.
Pour batter into a greased and lined 8-inch round cake pan. Bake at 350°F (175°C) for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Let cake cool completely. Mix glaze ingredients until smooth and drizzle over cake before serving.