Preheat oven to 350°F (177°C).
Grease a 6-inch round springform pan and line with parchment paper.
Add bananas, cocoa powder, eggs, and maple syrup to a blender.
Blend until completely smooth, scraping sides as needed.
Pour batter into the pan and smooth the top.
Bake for 60–70 minutes until set and slightly cracked on top.
Cool completely, then refrigerate for several hours to firm up.
Slice with a sharp knife and serve.
This 4 Ingredient Healthier Chocolate Cake becomes even richer and fudgier after chilling.