Heat the oven to 180C/160C fan/ gas 4. Oil a 30 x 24cm swiss roll tin and line with baking parchment. Put the eggs, vanilla and both sugars in a large bowl, and beat with an electric whisk for 5 mins, or until thickened and doubled in volume. The beaters should leave a thick trail when lifted out of the mixture.
Sift over the flour, baking powder, cinnamon and ¼ tsp salt, and very gently fold in using a large metal spoon. Pour into the prepared tin and bake for 10-15 mins until golden and springy. Leave to cool in the tin a little, then turn out onto a sheet of baking parchment dusted with icing sugar. Roll up from a longer end, along with the parchment, then leave to cool.
Toss the pears with the lemon juice in a bowl, then tip into a sieve set over a bowl to drain off any excess liquid. Beat together the mascarpone, double cream and 3 tbsp of the maple syrup until thick and spoonable. Tip the pecans into a food processor and blitz until finely chopped, then spread out on a large sheet of baking parchment.
When the sponge is completely cool, unroll and drizzle over the remaining maple syrup. Spread with three-quarters of the mascarpone mixture, then scatter over the pears and roll up again tightly. Spread the remaining mascarpone all over the outside of the roulade, then swiftly roll in the chopped pecans. Cut into thick slices and serve with an extra drizzle of maple syrup, if you like.