1. Prepare the lemon emulsion: place the lemon juice in a small saucepan and bring to a boil. Use a whisk to incorporate the cold butter cubes, a few at a time, beating vigorously. Whisk continuously until sauce is creamy.
2. Remove the saucepan immediately from heat and add the hot chili sauce, 15 mL (1 tbsp.) of tarragon, salt and pepper. Set aside.
3. Use kitchen scissors to open the lobster tail shells.
4. Divide the mâche onto the centre of 4 plates.
5. Cut the lobster tails diagonally into 4 or 5 thick slices and arrange them over the mâche. Add 10 tomato halves per plate, drizzle with lemon sauce to taste, and garnish with the remaining tarragon.

Chef's secret
The lemon sauce should be kept at a continuous boil during preparation. It's just at the end that it emulsifies and becomes perfectly creamy.