Instructions
Tap on the "Menu" button with your stylus to open the main menu. Tap on the "Village" button and select "Costolot's General Store" as your destination.
Scroll through Costolot's inventory with your D-pad and locate the listing for carrot seeds. Press "A" to purchase a carrot seed, and select an empty space in your garden to place the seed. Tap on the seed with your stylus and select the "Plant" option.
Open your menu and tap on your watering can to equip it. Target the carrot plant with your stylus to begin watering it. Hold your stylus against the screen to dispense water continuously, and remove the stylus from the screen to stop the water flow. Watch the water gauge above the plant and release your stylus before the meter is full to avoid overwatering.
Wait for your plant to mature, watering it as needed until it produces a carrot. Return to the village and enter Bart's Exchange. Purchase a Gold Tinker Ticket and tap on the carrot with your stylus to designate the tinkering target.
Wait for Bart the Tinker to appear in your garden. When Bart reaches the carrot, he will transform it into a carrot cake before he returns to his shop.