Preheat your oven to 210°C (fan-forced 190°C). Line a baking tray with baking paper.

Remove the rind from the bacon rashers and cut them into 2 cm pieces. Set aside. Thinly slice the onions and halve the cherry tomatoes.

Heat the olive oil and butter in a frying pan over medium-low heat.

Add the sliced onions and a pinch of salt. Cook, stirring every few minutes, for 25–30 minutes until the onions are deeply golden and jammy.

Add the balsamic vinegar, stir through, and cook for a further minute. Remove from heat and set aside. (You can do this step ahead of time.)

Toss the cherry tomatoes with 1 tbsp olive oil, thyme leaves, salt, and pepper on the lined baking tray.

Spread in a single layer and roast in the preheated oven for 15–20 minutes, until burst, jammy, and beginning to caramelise at the edges.

While the tomatoes roast, heat a dry frying pan over medium-high heat. Add the bacon pieces and cook for 3–4 minutes, stirring occasionally, until golden and just crispy. Transfer to a plate lined with paper towel to drain.

Place the puff pastry sheet on a second sheet of baking paper on a clean baking tray.

Using a sharp knife, score a 2 cm border all the way around the pastry — cut just halfway through, not all the way, so the border puffs up as a wall.

Prick the inner rectangle all over with a fork — this stops the centre puffing too much so it can hold the toppings.

Brush the border with the lightly beaten egg wash for a glossy, golden finish.

Par-bake the pastry in the oven (alongside or after the tomatoes) for 10 minutes at 210°C, until the border is just beginning to puff and turn pale gold.

Remove the par-baked pastry from the oven. If the centre has puffed, press it gently back down with the back of a spoon.

Spread the caramelised onion evenly over the inner rectangle of the pastry.

Scatter the roasted cherry tomatoes over the onion in an even layer.

Distribute the crispy bacon pieces evenly over the top.

Make 3 small wells in the topping using the back of a spoon, then carefully crack one egg into each well.

Return the tart to the oven and bake for a further 10–12 minutes, until the pastry border is deep golden and the egg whites are just set but the yolks are still runny — the eggs will look slightly wobbly at the centre when you pull them out; residual heat finishes them.

Season the baked tart with a little extra salt and cracked black pepper.

Warm the flatbreads in the residual oven heat for 1–2 minutes or directly over a gas flame for 30 seconds per side until lightly charred.

Slice the tart into 4 portions and serve immediately with the warm flatbreads on the side for scooping.