Preheat oven to 200 degrees. Line a baking sheet with a brown paper bag.
Make the salsa:
Place all of the ingredients (except the avocado) in a bowl, and stir to mix. Refrigerate in an airtight container until ready to serve, for up to 2 days.
Just before serving, add the avocado, and mix gently.
Cut the corn from the cobs into a large bowl and scrape the stripped cobs with the back of a knife (or a spoon) to release the juices into the bowl.
Place 2 cups of corn kernels into a food processor, and pulse several times, until the corn is slightly pureed but chunky. Transfer back into the bowl with the reserved corn kernels.
Mix the flour, cornmeal, onion, parsley, baking powder, baking soda, salt, cayenne and pepper with the corn.
Add the eggs, buttermilk and butter, and stir just to combine. (Do not overmix.)
Place a large skillet over medium heat until warm Add just enough olive oil and butter to cover the bottom, and heat until sizzling hot.
One heaping Tablespoon at a time, scoop the batter into the skillet. Flatten if necessary. Cooking in batches of 4 to 5 to avoid overcrowding, fry the cakes 1 to 2 minutes per side, until golden brown.
Drain on the lined baking sheet, and place in the oven to keep warm while cooking the remaining corn cakes. Serve warm with fresh salsa.