The first building in Rome to have a Baroque facade was the Church of the Gesù in 1584; it was plain by later Baroque standards, but marked a break with the traditional Renaissance facades that preceded it. The interior of this church remained very austere until the high Baroque, when it was lavishly ornamented.
Baroque architecture in Portugal enjoys a special situation and different timeline from the rest of Europe.
The buildings are single-room basilicas, deep main chapel, lateral chapels (with small doors for communication), without interior and exterior decoration, simple portal and windows. It is a practical building, allowing it to be built throughout the empire with minor adjustments, and prepared to be decorated later or when economic resources are available.
In fact, the first Portuguese Baroque does not lack in building because "plain style" is easy to be transformed, by means of decoration (painting, tiling, etc.), turning empty areas into pompous, elaborate baroque scenarios. The same could be applied to the exterior. Subsequently, it is easy to adapt the building to the taste of the time and place, and add on new features and details. Practical and economical.