Mix together the gram flour, baking powder and salt in a large mixing bowl, then make a well in the centre and pour in 450ml (¾ pint) lukewarm water and half the olive oil. Gradually whisk the wet ingredients into the dry to make a light batter. Leave to sit, covered, for 2 hours or even overnight.
Preheat the oven to gas 7, 220°C, fan 200°C. Heat the remaining olive oil in a 30 x 25cm (13 x 10 inch) roasting tin for 5 minutes until very hot. Carefully remove from the oven and pour the batter into the hot oil.
Scatter the red onion, olives, sun-dried tomatoes, chilli and thyme over the batter and bake for 15–20 minutes until set and starting to turn golden around the edges. Leave to sit for a couple of minutes before cutting into wedges.
