It meets the definition of "restaurant", so you could call it that. However, it seems like a relatively small and informal restaurant, so I'd prefer to call it a "cafe":

a usually small and informal establishment serving various refreshments (such as coffee) (M-W)

It is not a "stall", which typically is even smaller and has a divider between the employees and customers:

A booth, cubicle, or stand used by a vendor, as at a market. (AHD)

I speak Northeast U.S. English. Terminology may vary with dialect.

It meets the definition of "restaurant", so you could call it that. However, it seems like a relatively small and informal restaurant, so I'd prefer to call it a "cafe":

a usually small and informal establishment serving various refreshments (such as coffee) (M-W)

It is not a "stall", which typically is even smaller and has a divider between the employees and customers:

A booth, cubicle, or stand used by a vendor, as at a market. (AHD)

I speak Northeast U.S. English. Terminology may vary with dialect.

It meets the definition of "restaurant", so you could call it that. However, it seems like a relatively small and informal restaurant, so I'd prefer to call it a "cafe":

a usually small and informal establishment serving various refreshments (such as coffee) (M-W)

It is not a "stall", which typically is even smaller and has a divider between the employees and customers:

A booth, cubicle, or stand used by a vendor, as at a market. (AHD)

It meets the definition of "restaurant", so you could call it that. However, it seems like a relatively small and informal restaurant, so I'd prefer to call it a "cafe":

a usually small and informal establishment serving various refreshments (such as coffee) (M-W)

It is not a "stall", which typically is even smaller and has a divider between the employees and customers:

A booth, cubicle, or stand used by a vendor, as at a market. (AHD)

I speak Northeast U.S. English. Terminology may vary with dialect.