Heat the oven to 375°F. Oil a 9-by-5-inch metal loaf pan and line with a parchment sling.
Stir ricotta, panko, eggs, Parmesan, parsley, garlic, lemon zest, salt and pepper together and let stand for 5 minutes.
Fold in chicken just until combined and transfer to the pan, smoothing the top gently.
Bake for 55 to 65 minutes until the center reaches 165°F. Rest in the pan for 10 minutes.
Melt butter in a small saucepan over low heat and stir in lemon juice. Lift the loaf with the sling and brush the top with the lemon butter.
Cut into 8 slices with a sharp knife, supporting each slice with a spatula.