Freeze the bananas, unpeeled, for at least 2 hours or up to overnight.
Thaw bananas for 45 minutes to 1 hour, then peel and puree along with the lemon juice in the work bowl of a food processor for 10 to 15 seconds.
Add the corn syrup and vanilla bean seeds and turn the food processor on. Slowly pour in the cream and continue processing until smooth.
Chill the mixture in the refrigerator until it reaches 40°F, which should take about 3 hours. Transfer the mixture to an ice cream maker and process according to the manufacturer's instructions.
Transfer soft-serve consistency ice cream to an airtight container and harden in the freezer for 3 to 4 hours before serving.