Place your cherry tomatoes on a large baking tray and drizzle with olive oil, salt and pepper. Toss to combine, then arrange your sausages on the same tray.
Roast for 15 mins at 180°C/350°F.
In a large jug, whisk together your buttermilk, butter and egg.
Sift your cornmeal, plain flour, baking powder, bicarbonate of soda and salt in a large bowl. Add your brown sugar, diced jalapeno, cheddar and spring onions and stir to combine. Make a well in the middle and pour in your wet ingredients. Whisk together until you just have a smooth mixture.
In a large buttered baking dish, pour half your mixture. Sprinkle with most of the bacon and tomatoes, then pour on the rest of the mixture. Top with sausages, your remaining tomatoes and sliced jalapeños. Sprinkle with remaining cheddar and bake for 25-30 mins at 200°C/400°F.