For the Vinaigrette
2 teaspoons apple cider vinegar
1 tablespoon fresh-squeezed lime juice
2 tablespoons olive oil
2 tablespoons vegetable oil
3/4 teaspoon kosher or sea salt, or more to taste
1/2 teaspoon oregano
1/2 teaspoon brown sugar
1/4 teaspoon freshly ground black pepper
1. To make the vinaigrette, pour the vinegar and lime juice in a small bowl. Add oregano, salt sugar and black pepper. Pour the oils in a slow stream, whisking with a whisk or fork to emulsify. The vinaigrette can be made a day ahead of time, just emulsify before using.
2. To toast the pumpkin seeds, place them in an already hot small saute pan, set over medium heat. Stir often, being careful not to burn them, until you start to hear popping sounds (similar to pop corn), and they begin to acquire a nice tanned color, about 4 to 5 minutes later. Remove from heat and place in a bowl.
3. In a separate bowl, gently mix the avocado chunks, hearts of palm slices, corn kernels, cherry tomatoes and red onion with the vinaigrette. Sprinkle with the toasted pumpkin seeds and serve.