chopped Italian (flat leaf) parsley, chives or dill for garnish
3 English muffins, split and toasted (optional)
Preheat oven to 400 degrees. Line a rimmed baking sheet (large enough to comfortably hold the tomatoes in one layer) with parchment paper.
Cut the tops off the tomatoes. Remove the core and seeds (I use a grapefruit spoon). Place tomatoes upside down on paper towels to drain.
In a blender or food processor, combine the egg yolks, lemon juice, balsamic vinegar, salt and pepper. Process until well blended. Set aside (leave mixture in the blender).
Heat butter and Gremolata Olive Oil in a small saucepan over medium heat, just until butter is melted, stirring constantly. With the blender/food processor running, VERY slowly pour in the warm butter mixture until blended. Taste and adjust lemon juice, salt and pepper as needed. Set aside. (See Tips below if your sauce it too thick or too thin.)
Place tomatoes cut side up on prepared baking sheet. Spray or brush with olive oil. Bake for 10 to 12 minutes, or until hot.
Remove from oven; pour off any moisture that may have accumulated in the tomatoes. Sprinkle with salt and pepper. Carefully put an egg inside each tomato. (Note: you can also beat the eggs first, then pour them into the tomatoes.) Place back in oven and bake until desired doneness – around 10 minutes for runny yolks, or 14 minutes for fully cooked.
Place each cooked tomato on a small dinner plate, in a ramekin or in a small bowl. (Option: place tomatoes on toasted English muffin halves.) Can also place all the tomatoes together on a serving platter. Spoon Hollandaise sauce over the top. Sprinkle with chopped parsley, chives or dill. Pass extra sauce on the side. Serve immediately.
Make ahead: sauce can be made up to 24 hours ahead, cooled, covered and refrigerated. To rewarm, heat in the microwave for 10 seconds; whisk. If very thick, whisk in 1 tablespoon hot water. Place back in microwave and heat in 7 to 8 second increments, whisking in between, until just barely warm (usually just takes around 2 more times). Add additional water as needed. Don’t overcook – it could separate and/or eggs could scramble.
Note on lemon balsamic vinegar: it can be found in specialty stores or on line. You can also substitute white balsamic vinegar and add a bit more lemon juice (to taste).
Note on gremolata olive oil: it can be found in specialty stores or on line. You can substitute extra virgin olive oil and a bit of lemon zest.
Note on large eggs: the size of eggs to use depends on the size of your tomatoes. A softball size tomato will hold a large egg; for smaller tomatoes (like those on the vine), I recommend using medium size eggs.
Tip on how to thicken Hollandaise Sauce: if your sauce is thin or runny, while the eggs are baking, place sauce in a small saucepan over a low simmer and heat, stirring/whisking. It will thicken as it gets hot. Watch carefully – it could separate and/or the eggs in it could scramble.
Tip on how to thin Hollandaise Sauce: Whisk in 1 tablespoon hot water. Keep adding more water as needed until it reaches desired thickness.