Prepare nuts: pre-prepare the parchment, sprinkle it with olive oil. In a frying pan, heat the butter and sugar on medium-high heat, heat until the sugar is completely melted and starts to get dark, then pour half peeled walnuts (or pecans) and gently stir until they are completely covered with no sugar syrup. Then remove from the pan and place on a parchment to pour caramel.
Prepare the filling: on the bottom of a salad bowl, combine the orange zest with its juice, vinegar, mustard and butter, salt and pepper to taste.
Wash apples, cut into thin slices, add to the bowl to the filling with a mixture of lettuce, all carefully mix. Sprinkle nuts (they have to break into smaller pieces), stir again and serve.