1. Lightly rub a cookie sheet with olive oil; set aside. Heat a large saucepan over low heat; add butter and sugar. Simmer a couple of minutes, stirring occasionally, until sugar has completely dissolved and the mixture darkens. Gently stir in pecans until well-coated; be careful not to splash yourself. Transfer nuts to cookie sheet; use the back of a spoon to separate them into one layer. Allow to cool so caramel hardens.
2. Combine orange zest, orange juice, mustard, vinegar, and oil in a large salad bowl; stir well with a whisk. Have a taste--you want a nice balance between the vinegar and the oil. Adjust, if needed, and season with salt and pepper.
3. Add apples and greens to dressing. Break cooled pecans apart; add half to bowl. Toss mixture gently with your hands. Top with remaining crumbled pecans. Divide among 6 plates; serve.