For the panna cotta: dissolve the gelatin powder in 1/4 cup/60 ml of cold water. Let it rest for 3 minutes.
Put the milk and cream in a saucepan. Add the vanilla seeds and pod, lemon zest and honey (keep the lemon juice for the caramel). Slowly bring to a boil. Add the gelatin and continue cooking until it's completely dissolved, about 2 minutes. Remove from heat and let zests infuse for 5 minutes.
Strain through a fine sieve and divide into 4 glasses. Put it in the refrigerator and let sit for at least 4 hours.
For the caramel: Heat the powdered sugar in a saucepan on low heat until it melts and turns into a golden color, about 5 minutes. Add in butter, lemon juice, and cream. Turn off the heat, and let it sit for 2 minutes.
For serving: Serve the panna cotta with the lemon caramel sauce and supreme of Meyer lemon to garnish.