Make the pork: Preheat the oven to 375F. In a medium bowl, whisk the annatto-seed paste with the vinegar and 3 cups of water. Season with salt and strain the mixture through a fine-mesh strainer. Line a roasting pan with the banana leaves (or aluminum foil), leaving enough space hanging over the rim to wrap the leaves around the pork shoulder.
Place the pork shoulder on the banana leaves and pour the strained sauce over it. Add the onion, garlic cloves and cinnamon-stick pieces and wrap the leaves over the pork. Cover the pork with aluminum foil and roast until tender and falling off the bone, about 4 hours, 30 minutes.
Make the ensalada: Toss the cabbage and radishes together with the lime juice. Season with salt and set aside.
Make the cured onions: In a medium bowl, combine the red onions, vinegar, salt and cinnamon sticks. Set aside to cure while the pork is cooking.
When the pork is finished, remove from the oven and set aside for 10 minutes. While the pork is resting, toast the tortillas in a hot skillet. Serve warm with pieces of pork, the cabbage salad and the cured onions.