Combine the 1/4 cup cream, 1/2 cup milk and 1-2 tbsp lavender in a small saucepan over medium heat. Cook until it just begins to simmer; remove from the heat and cool slightly.
Preheat the oven to 325F (163C) . Spray with cooking spray or butter and flour a 9×5 inch loaf pan or a large round cake pan*.
Cream the 6 tbsp room temperature butter and 3/4 cup sugar together with an electric mixer or stand mixer, stopping to scrape down the sides in the middle.
Beat in the 2 eggs, one at a time, until the batter is light and fluffy; again stopping halfway to scrape down the sides of the bowl.
Mix in 1 tsp vanilla and 1 tbsp lemon zest until just combined.
In a separate bowl, combine 2 cups flour, 2 tsp baking powder, and 1/2 tsp salt.
Add the flour mixture and the lavender cream mixture into the butter mixture a little at a time, giving it a mix with each addition. Mix till just combined.
Pour into the prepared pan and bake for 45-50 minutes or until a tester inserted in the middle comes out mostly clean.
Let the cake cool in the pan a few minutes before removing from the pan and transferring to a rack to cool completely.