Chipping I did some experimenting last night and inadvertently created something that would be perfect for you!
I set out to make bacon, shallot and Gruyere tart - the filling (apart from those three ingredients) is egg and cream. But I forgot to include the eggs 
Obviously you can't eat the bacon, but I reckon that if you added a bit more shallot it would make a lovely cheese and onion tart:
Shallot and Gruyere Tart (A BIWI special!)
serves 6
225g ground almonds
55g butter, diced
1/2 teaspoon salt
for the filling:
25g butter and a splash of oil (this stops the butter burning)
2 cloves of garlic, finely chopped (or use a garlic crusher)
150g shallots, thinly sliced (this will be 3-4 echalion shallots)
dried oregano
100g Gruyere cheese, grated
300ml double cream
salt and freshly ground black pepper
Preheat the oven to 180C/350F/GM4
To make the pastry, mix the almonds, butter and salt until it forms a dough. This is easiest done in a food processor. Keep processing it until it starts to come together into a ball.
Press the dough with your hand/fingers into a 20cm flan tin or dish. Push the pastry up the sides of the tin as well. There is quite a lot of filling, so it's important to get the pastry as far up the sides as you can.
Prick the base of the flan all over and bake in the oven for 20 minutes or until set and golden brown. (It's better if it's cooked longer, as it hardens up a little more - just keep an eye on it and make sure it doesn't burn)
While the dough is cooking, saute the shallots and garlic in the butter and oil, till soft. Season with salt and pepper and about a teaspoon of dried oregano. Leave to cool.
Tip the shallots into the flan case and add the cheese, season with black pepper, then pour over the cream. (It's a good idea to put the flan tin onto a baking tray, as it is likely to be very full, and this makes it easier to get into the oven without spilling anything)
Bake for 25-30 minutes, or until golden brown and just set. Serve warm or cold.
27.35g carbs for the whole lot. If you serve 6 people, this will be 4.6g per person.