Preheat oven to 350F. Lightly grease and flour a 9-inch cake pan and set aside.
Combine milk and lavender in a small saucepan. Heat over medium heat, stirring frequently until milk is steaming (do not boil). Remove from heat and allow to steep 20 minutes. Strain milk and discard lavender.
Place butter and sugar in a large bowl (or a stand mixer fitted with paddle attachment) and use an electric mixer to beat on medium speed 2-3 minutes until smooth and creamy.
Add eggs one at a time to butter mixture while beating constantly on medium speed, beating well after each addition. Mix in honey, lemon juice, zest, and vanilla until smooth.
In a medium separate bowl, combine flour, baking powder, and salt. Working in increments, fold half of flour mixture and half of lavender milk into liquid mixture until smooth and repeat until all the flour and milk has been added and batter is smooth.
Scrape half of batter in prepared pan. Spoon lemon curd on top and smooth into an even layer. Scrape remaining batter into pan and smooth top. Set aside for a moment.