Preheat oven to 180c.
Cut pumpkin into approximately 2cm cubes. Place in a baking tray and toss with a generous splash of extra virgin olive oil and season well. Place in the oven for 30 minutes and roast till just tender. Remove and set aside.
Place the besan flour in a bowl and make a well in the centre. Add the water and whisk well removing any lumps. Cover the bowl with a plate to seal the top and set aside at room temperature for at least 4 hours (or overnight in fridge).
20 - 30 minutes prior to cooking preheat your oven to 225c fan-forced and place a oven proof round skillet pan in to heat.
After resting the farinata batter, remove the plate from the top of the bowl and skim off any of the foam tht has formed there (this will help keep the gas production down by your friendly gut microbes). Add in 1 tablespoon of the extra virgin olive oil, 1 teaspoon of the chopped rosemary and the sea salt and whisk through.
Take the baking pan out of the oven very carefully using thick oven mits and then add in the remaining extra virgin olive oil. Swirl this around the pan, it should smoke a little which is fine. Now super carefully pour the farinata batter into the hot pan allowing it to dispurse evenly. Top with the pumpkin cubes and finish with the remaining rosemary. Place back in the oven for 10 - 12 minutes until the farinata is golden all over and crisp around the edges.
Remove from the oven and slice into quarters. Serve immediately dressed liberally with more salt, drizzle of extra virgin olive oil and any left over chopped rosemary.