For the crackers, preheat the oven on CircoTherm to 180°C and line two baking trays with baking paper. Sift the flours and baking powder into a medium size bowl. Stir in the salt and the seeds and make a well in the centre. Add the oil and the water and mix together to a workable dough being careful not to over mix. Flatten into a round shape then roll the dough out between two pieces of baking paper to approximately 3mm in thickness. Using a 6cm round cutter, cut the dough and place onto the prepared trays. Cook on shelf positions 1 and 3 for 13 to 15 minutes or until lightly golden and cooked. Leave the crackers to cool completely on the tray before storing in an airtight container.
Combine the rock salt, sugar and dill in a bowl. Place 2 large pieces of plastic wrap onto a board and spread half of the rock salt mixture in the shape of the salmon onto the plastic wrap. Place the salmon, skin side down on top. Spread the remaining salt mixture over the salmon to coat completely. Wrap the salmon tightly in the plastic wrap and place into a shallow glass dish. Place a small board on top of the salmon then weight with 2 x 400g cans and refrigerate for 12 hours.
Remove any excess liquid from the dish and turn the salmon over. Replace the weights and refrigerate for a further 12 hours. Unwrap the salmon and brush off the salt mixture, wiping with paper towel. Place the salmon into a clean glass dish and refrigerate until ready to use.
Line a strainer with some muslin cloth or food grade chux and place over a bowl. Place the yogurt into the strainer and refrigerate for 6 to 8 hours to drain excess liquid. Place the drained yogurt into a bowl then combine with the remaining ingredients and mix well.
To serve, slice the gravlax salmon thinly. Spread the dill yogurt onto a cracker and top with a slice of salmon. Serve with pickled cucumber, red onion and capers.