Knead the dough
15 minMix the flour, yeast, sugar, and lemon zest. Add the warm milk and eggs, bring the mixture together, and knead for 5 minutes. Sprinkle in the salt, then add the butter a little at a time. Knead for 8 more minutes, until the dough is smooth, glossy, and elastic. The dough should be soft and slightly sticky; do not make it firmer by adding flour. Cover and leave it to rise.