Step 1

Fill a fondue pot (or small slow cooker) with very hot water and set aside to warm.

Step 2

Heat oil in a large skillet over medium heat. Add fennel and onion and cook, stirring often, until translucent, 8 to 10 minutes. Add tomatoes, salt and pepper; cook, stirring occasionally, until any liquid evaporates, 2 to 4 minutes. Remove from heat.

Step 3

Combine both cheeses, flour, fennel seeds and cayenne in a medium bowl.

Step 4

Heat wine in a medium heavy-bottomed saucepan over medium heat until hot, but not boiling. Add the cheese mixture a handful at a time, stirring until melted before adding more. Remove from heat and stir in the vegetable mixture.

Step 5

Drain and dry the fondue pot (or slow cooker). Pour in the fondue and keep warm over a low flame (or on the warm setting) to serve. Stir in a teaspoon or two of flour if your fondue starts to separate.