Grease a 4- to 6-quart slow cooker with the olive oil.

In a bowl, whisk the eggs, heavy cream, sea salt, and black pepper.

In the prepared slow cooker pot, arrange the asparagus spears in a single layer. Pour the egg mixture over the asparagus.

Cover and cook on LOW for 2 hours, until the eggs are cooked through.

Serve the omelet topped with Parmesan cheese, cherry tomatoes, and red onion slices.