You can find the OOTB onet.xml of blog site template at the following location

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\15\TEMPLATE\SiteTemplates\Blog

I was surprised that there is not any default.aspx page for this blog template which was available in SharePoint 2010. The OOTB SharePoint 2013 blog site template folder has missing default home page.

I have imported the Onet.xml file in visual studio; it contains the following web features.

<WebFeatures>
        <!-- TeamCollab Feature -->
        <FeatureID="00BFEA71-4EA5-48D4-A4AD-7EA5C011ABE5" />
        <!-- MobilityRedirect -->
        <FeatureID="F41CC668-37E5-4743-B4A8-74D1DB3FD8A4" />
        <!-- Blog feature -->
        <FeatureID="FAF00902-6BAB-4583-BD02-84DB191801D8" />
        <!-- MDS -->
        <FeatureID="87294C72-F260-42f3-A41B-981A2FFCE37A" />
</WebFeatures>

After few minutes I realised that there is a feature in 15 hive which called “Blog Home Page”.

You can find the “Blog home page” feature.xml at the following location

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\TEMPLATE\FEATURES

You need to reference this feature in blog site definition to make sure that when a user create site based on your custom blog template, it activates this feature which create home page for blog site.

The resulting Web feature node in blog onet.xml will look like this

<WebFeatures>
        <!-- TeamCollab Feature -->
        <FeatureID="00BFEA71-4EA5-48D4-A4AD-7EA5C011ABE5" />
        <!-- MobilityRedirect -->
        <FeatureID="F41CC668-37E5-4743-B4A8-74D1DB3FD8A4" />
        <!-- Blog feature -->
        <FeatureID="FAF00902-6BAB-4583-BD02-84DB191801D8" />
        <!-- MDS -->
        <FeatureID="87294C72-F260-42f3-A41B-981A2FFCE37A" />
       <!-- Blog Home Page feature -->
       <FeatureID="E4639BB7-6E95-4E2F-B562-03B832DD4793"/>
 </WebFeatures>