A treacle tart is something that I have never eaten. It is a very English dessert, and the closest American dessert I can imagine would possibly be Shoo Fly Pie.
A tart is generally a very shallow pie, sometimes topped with a crust. A treacle tart is a buttery crust filled with a mixture of Golden Syrup, lemon zest, and breadcrumbs. Golden Syrup (of which Lyle’s is a popular brand) is similar to American Karo corn syrup. For a stronger molasses taste, dark corn syrup or molasses can be added to taste.
I believe I may bake a Treacle Tart tomorrow, and I imagine it will go down perfectly with a nice cup of tea.