In a separate bowl, whisk together the flour and salt. Set aside. Cut the the cold butter in cubes, add the sugar and mix well with your clean hands. Incorporate the egg yolks and mix well. Add flour mixture all at once and mix just until it forms a ball. Don't overwork or pastry will be hard when baked. Flatten the dough into a circle, cover the pan with it to get uniform thickness and put it in the oven for 15 mins at 450 C
Place the sugar and water in a large saucepan, over medium heat, and stir until the sugar completely dissolves. Add the chunks of rhubarb and reduce the heat to a low. Cover and simmer (about 5 - 15 minutes) until the rhubarb is tender and soft. Remove the pan from the heat and let stand until the rhubarb has cooled to lukewarm. Cut the strawberries in slices or use the frozen berries. Take the semi-baked crust out of the oven, cover it with rhubarb paste and strawberries it put it back intro the oven for 10 min more.
Meanwhile beat egg whites into soft peaks, add sugar, lemon juice (an advice form my mom for a fluffy meringue), then beat into stiff peaks. Make sure you add the sugar after soft peaks are formed. If added before that, the egg whites could stretch too much which prevents a stiff peak altogether. Spread the meringue over rhubarb topping and bring it back to the oven for 12 min more.