Cut the tomatoes into slices through the middle (ie from top to bottom or vice versa). Remove any tough core pieces. Lay them out on a board, baking sheet or tray and sprinkle over the salt. Set aside for around 10-20 minutes while you roll the crust etc.
Preheat the oven to 375F/190C. Lime a large baking sheet with parchment.
Roll out the pastry on a lightly floured surface into a circle approx ⅛in/3mm thick (it doesn't have to be perfect) with a diameter of around 10-11 inches (25-28cm). Transfer to a lined baking sheet/tray.
Sprinkle the parmesan over the pastry, leaving around 1in/2.5cm around the edge without cheese on it. Break up around ½ of the goat cheese into small pieces and dot over the parmesan.
Pat dry the tomato slices and arrange them over the cheese on the pastry. It's fine to make a couple layers, and if anything stacking a little higher towards the middle. I tend to hold back the top and bottom pieces and cut them up to fill gaps later.
Break up the rest of the goat cheese and put little pieces over the tomatoes here and there. Sprinkle over the marjoram.
Fold in the edges of the pastry to cover the tomatoes slightly, making slight folds as you go. It doesn't matter if the edges are uneven, but try to seal any cracks to save it leaking. If you have any pieces that look slightly empty towards the edges, cut off parts of the top pieces of tomato you saved and tuck them under the pastry to make the filling more even.
Place the galette in the oven and bake for approximately 20 - 25 minutes until the pastry is golden brown and gently crisp. Leave to cool a minute before serving (can be served both warm or room temperature).