Measure out 6 circles larger than 6 tartlet tins. Spray tartlet tins with spray oil and dust with flour. Line tin with pastry, and trim edges. Refrigerate for 20 minutes.
Preheat oven to 180 degrees C. Line pastry with paper, and fill with dried rice or pastry weights. Bake for 15 minutes, then remove paper and beans and cook a further 15 minutess, until dry and lightly golden. Cool completely.
Meanwhile, heat oil in a large frying pan, add onions and a pinch of salt. Cook over medium-low heat for about 35 minutes, until a deep golden colour. Season well with salt and pepper and transfer to a bowl to cool.
Spread cooled onions over pastry base. Sprinkle cheese over, then thyme leaves. Lightly whisk eggs and cream together, then pour over the filling. Add 2-3 small dollops of Anathoth Farm Sweet Chilli Relish on each tart.
Stand on a tray and bake for 30-35 minutes, until set and golden.