Pre-heat the oven to 140 C / 284 F. Line a large baking tray with greaseproof paper. Add the tomatoes, salt, olive oil, balsamic vinegar and garlic to a bowl and mix to combine. Arrange the tomatoes, cut side up, on the baking tray and slow roast for 1 ½ to 2 hours. They’re done when wilted and lightly brown around the edges.
For the pesto, finely chop, separately, the almonds, arugula and tarragon. Mix everything together in a bowl and add the salt, garlic clove, lemon juice and olive oil. Mix well to combine. Have a taste and adjust the seasonings if needed be. Alternatively, and instead of chopping up the ingredients by hand, you can use a food processor to blend them up.
Raise the oven temperature to 200 C / 390 F.
Sift the chickpea flour, salt and za’atar to a bowl. Slowly pour in the water, whisking vigorously to avoid any lumps. Let the batter sit, covered, for 30 minutes to 1 hour at room temperature.
In the meantime, grease one 25 cm / 10 inch round baking dish with olive oil and put it in the middle third of the oven for at least 10minutes. After that time take, very carefully, the pan out of the oven and pour the batter into it. Return the pan to the oven for 20-25 minutes, or until the chickpea pancake is golden brown on top. You can finish it (as I did) on the broiler for the last 5 minutes of cooking to encourage even browning.
To assemble, cut the socca into 4 or 6 equal slices. Spread the pesto on each of the slices, add a generous amount of arugula on top as well as 2 to 3 tomato quarters. Drizzle a bit more pesto on top of the tomatoes and finish off with plenty of toasted silvered almonds.