Peel and roughly chop the shallot into small pieces.
Crush the peppercorns with the back of a knife.
Put the shallot, bay leaf, peppercorns, tarragon and vinegar into a small saucepan.
Place the saucepan over a medium heat and allow the liquid to evaporate until about a tablespoon of liquid remains.
Scrape the mixture into a sieve with a heatproof bowl underneath that you will make the sauce in.
Put the butter in a another saucepan and melt over a medium heat or in the microwave in 10 second bursts on high.
Remove the milk solids and impurities that float to the top with a spoon.
Add the egg yolks to the strained liquid and whisk for 2 minutes.
Set the bowl over simmering water and continue whisking for a further 2 minutes until the mixture is pale and thick.
Take the saucepan off the heat and whisk in a small amount of butter at first.
Now add the remaining butter in a steady stream, whisking continuously.
Stir in the tomato purée and season to taste.
Serve immediately with your favourite steak.