In order to make (or bake) a Cake, you will need:
1. 9 iron ingots: can be found in caves as ore and obtained by a stone pickaxe. You will also need a furnace, made of cobblestone, and fuel (coal, wood, etc.) to smelt the ore into ingots.
2. 2 sugar: you will need 2 sugarcane, which are found usually near lakes and oceans. Once obtained, you can craft it into sugar using your inventory crafting slots.
3. 1 egg: dropped by chickens every 5-10 minutes. You can lure a chicken into a pen or compartment using seeds, and wait until it drops it. Coincidentally, is it a chicken or a duck?
4. 3 wheat: can be farmed using seeds, and can also be found in village farms, and woodland mansion farm rooms.
Once all of the above items have been obtained, you can craft a cake using a crafting table. Once crafted, this achievement should pop. If not, place it on the ground.