Prepare the Dough: Spread out the flour on your workspace, create a well in the center, and add the 4 large eggs and extra egg yolk. Gently beat the eggs, incorporating the flour, and knead until smooth and elastic. Wrap in cling film and rest in the fridge for 1 to 3 hours.
Prepare the Filling: Boil the spinach until wilted, drain, and squeeze out excess water. Mix spinach, ricotta, grated nutmeg, and zest of 1 lemon in a bowl. Season with salt and pepper.
Form the Ravioli: Roll out the dough into thin sheets, laminate, and place spoonfuls of filling on a sheet. Cover with another sheet, seal around the filling, and cut into individual ravioli.
Cook the Ravioli: Melt butter in a skillet, add sage until crispy. Cook ravioli in boiling salted water for 2-3 minutes until they float. Drain and add to skillet with brown butter and sage. Squeeze juice of 1 lemon over the top, toss, and serve.