Amarillo has started life as a 30-cover pop-up at Lost in the Lanes café on Nile Street, with plans to take it permanent at a later stage.
Swainson is cooking from an open kitchen, serving pintxos and selection of sharing plates, including two fish dishes, two meat, two veg, two sides and two deserts.
Samples from the menu include a black rice, with cuttlefish and ink cracker for £11; and a beef bavette, confit tomato, and burnt onion for £14.
Pintxos, meanwhile, include a cold tomato and egg emulsion, with serrano ham, on bread with parsley; and nachos with raw salmon, soy dashi, and siracha.
Amarillo also has its own take on tiramisu using the coffee served at Lost in the Lanes, from Hasbean coffee roastery.
The cuisine is inspired by the Spanish modernist style, with Asian influences, though Swainson said he didn’t want to be pigeon-holed as a 'Spanish or tapas restaurant'.
“It’s an environment that’s nice to be in- there’s no airs and graces. Come in, have fun, and eat some great food in a social environment," says Swainson.
"People can come in and feel relaxed, with some reasonably priced food and wine.
“This is a venture to let people know who I am, and I don’t want the stigma of fine-dining food to get in the way of that.”
Swainson has been cooking for nearly 18 years in kitchens including the Michelin-starred L'Ortolan in Reading, Seaham Hall in County Durham, Le Becasse in Ludlow and Chewton Glen in Hampshire.
He led The Samling Hotel in Cumbria to a Michelin star, before taking over from Matt Gillan at The Pass, an intimate chef’s table restaurant at the South Lodge Hotel near Horsham.
Amarillo is running evening service this Friday and Saturday, with hopes to make it a four-day operation.