1. For the pears, peel and finely grate the ginger. Split the vanilla pod and scrape out the seeds, then place everything in a saucepan. Add 400 g of sugar and 700 ml of water. Bring to a boil, then let simmer for a few minutes to develop the flavors.
2. Using a spoon, gently lower the pears into the hot liquid and simmer for 10 minutes, until tender. Remove the pears from the liquid and let cool.
3. Line the base of a 25 cm springform cake tin with parchment paper.
4. Mix the remaining 150 g of sugar and 100 ml of water in a saucepan and place over high heat, simmering for about 15 minutes until it becomes a dark golden brown. Stir in the butter until it forms a caramel, then pour it into the cake tin.
5. Slice the cooled pears and carefully arrange them in the hot caramel.
6. Preheat the oven to 180°C. For the cake, whisk the butter and sugar together until smooth. Add the eggs one at a time, mixing well after each addition. Add the almonds and mix to combine. Pour the cake mixture over the pears and bake in the oven for 30 to 35 minutes, or until the cake is firm to the touch. Let cool in the tin, then remove and carefully flip it over to serve.