Place the steaks on a board and
trim any excess membrane. If the
steaks are not even in thickness,
cover with cling film or baking paper
and bash with a rolling pin
until they are.
Measure the marinade ingredients
into a bowl and mix well. Season
with salt and black pepper, add the
steaks and turn in the marinade to
coat. Leave to marinate for
about 1 hour.
Preheat the oven to 220°C/Fan
200°C/Gas 7. Place the potatoes,
onions and 2 tablespoons of the
olive oil in a single layer in a large
roasting tin. Season and toss
together. Roast in the oven for about
25 minutes, or until the potatoes are
lightly golden.
Mix the crushed garlic and thyme
together in a small bowl and sprinkle
over the potatoes and onions. Push
them to one end of the tin and place
the tomatoes cut side up on the
other. Drizzle the tomatoes with the
remaining oil and the balsamic
glaze. Return to the oven for 8
minutes, or until the tomatoes are
just soft.
Meanwhile, heat a large frying or
griddle pan until very hot. Add the
steaks and fry for 1–2 minutes on
each side. Spoon the excess
marinade over each steak before
turning. Transfer to a warm plate to
rest for a few minutes. Scrape any
black pieces from the pan and
discard. While the steak is resting,
add the butter to the pan and toss in
the spinach leaves. Cook over a high
heat for a few minutes until wilted.
Season the spinach and spoon
into the centre of a long platter. Slice
the steak into long strips and
arrange on one side. Spoon the
potatoes and tomatoes on the other
and serve.