Preheat the oven to 350 F. Wrap the tortillas in aluminum foil and bake for 15 minutes. Set aside.
In a bowl, massage the extra virgin olive oil and a pinch of salt into the kale. Set aside.
If the walnuts are not toasted, put them on a small baking dish in the oven for the last 5 minutes of the tortilla baking.
In a large saute pan, heat the butter over medium heat.
Add the onions and saute for 2-3 minutes.
Then add the garlic to the onions and saute for 2 more minutes.
Add the apples to the pan, saute for 2 minutes.
Pour the honey in the pan, and stir to coat the apples and onions. Salt and pepper to taste, including the red pepper flakes if desired. Saute 2 more minutes, then remove from heat.
Assemble the tacos by putting the kale in each tortilla, then the apple onion mixture. Top with walnuts and cheese, and drizzle sparingly with balsamic vinegar.
Eat immediately.