Pour the buttermilk over the oatmeal and leave to swell for one night with the lid closed. Knead in the honey and butter with the dough hook of the hand mixer. Add the eggs one by one and mix them in.
Season the dough with sea salt and lemon zest. If it is too thick, add more buttermilk until it thickens.
Grease the waffle iron with a brush. Drop the batter in with a small ladle and bake waffles in order until golden brown. Bring the waffles to the table fresh.