Preheat the oven to 375°.
Drain a can of artichoke hearts and place them in the food processor. Pulse that about 5 times until the artichoke hearts are smaller and all the same size.
Put the cream cheese in the food processor, breaking it into chunks as you do so it's easier to blend together. Pulse that 5 times.
Defrost the spinach and wring it out to get rid of any excess liquid. To do this, put the spinach in a kitchen towel and wring out all the liquid over the sink. Add the drained spinach leaves to the artichoke and cream cheese mixture. Pulse 5 more times.
Add the mayonnaise, sour cream, parmesan, and garlic powder to the food processor. Pulse another 5 times or more until the texture you would like is reached. It should still be pretty chunky so there is some texture to the dip.
Pour the dip into an oven safe baking dish and top with the cheddar cheese. Bake for 15 minutes until the top is bubbly and the cheddar is starting to brown. Serve immediately.